Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.70	13.820%	$190.8761	$190.88	$190.90	$190.90
Purchase #2	$223.51	6.217%	$237.4056	$237.41	$237.40	$237.40
Purchase #3	$103.76	10.264%	$114.4099	$114.41	$114.40	$114.40
Purchase #4	$97.35	11.546%	$108.59	$108.59	$108.60	$108.60
Purchase #5	$225.84	6.487%	$240.4902	$240.49	$240.50	$240.50
Purchase #6	$211.69	5.494%	$223.3202	$223.32	$223.30	$223.30
Purchase #7	$237.31	13.373%	$269.0455	$269.05	$269.05	$269.00
7 purchase totals =	$1,267.16		$1,384.1375	$1,384.15	$1,384.15	$1,384.10