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	$178.89	6.415%	$190.3658	$190.37	$190.35	$190.40
Purchase #2	$99.38	5.791%	$105.1351	$105.14	$105.15	$105.10
Purchase #3	$171.90	7.448%	$184.7031	$184.70	$184.70	$184.70
Purchase #4	$40.32	5.447%	$42.5162	$42.52	$42.50	$42.50
Purchase #5	$55.72	4.143%	$58.0285	$58.03	$58.05	$58.00
Purchase #6	$222.27	12.132%	$249.2358	$249.24	$249.25	$249.20
Purchase #7	$215.54	3.614%	$223.3296	$223.33	$223.35	$223.30
7 purchase totals =	$984.02		$1,053.3141	$1,053.33	$1,053.35	$1,053.20