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	$67.57	7.600%	$72.7053	$72.71	$72.70	$72.70
Purchase #2	$242.50	3.218%	$250.3037	$250.30	$250.30	$250.30
Purchase #3	$206.54	10.623%	$228.4807	$228.48	$228.50	$228.50
Purchase #4	$106.41	7.823%	$114.7345	$114.73	$114.75	$114.70
Purchase #5	$144.87	11.290%	$161.2258	$161.23	$161.25	$161.20
Purchase #6	$107.88	11.589%	$120.3822	$120.38	$120.40	$120.40
Purchase #7	$190.33	6.384%	$202.4807	$202.48	$202.50	$202.50
7 purchase totals =	$1,066.10		$1,150.3129	$1,150.31	$1,150.40	$1,150.30