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	$65.26	9.573%	$71.5073	$71.51	$71.50	$71.50
Purchase #2	$173.80	4.696%	$181.9616	$181.96	$181.95	$182.00
Purchase #3	$41.28	6.691%	$44.042	$44.04	$44.05	$44.00
Purchase #4	$175.62	9.169%	$191.7226	$191.72	$191.70	$191.70
Purchase #5	$177.62	4.412%	$185.4566	$185.46	$185.45	$185.50
Purchase #6	$223.54	12.269%	$250.9661	$250.97	$250.95	$251.00
Purchase #7	$162.75	7.345%	$174.704	$174.70	$174.70	$174.70
7 purchase totals =	$1,019.87		$1,100.3602	$1,100.36	$1,100.30	$1,100.40