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	$164.72	12.463%	$185.2491	$185.25	$185.25	$185.20
Purchase #2	$221.89	4.502%	$231.8795	$231.88	$231.90	$231.90
Purchase #3	$222.32	12.355%	$249.7876	$249.79	$249.80	$249.80
Purchase #4	$53.73	3.839%	$55.7927	$55.79	$55.80	$55.80
Purchase #5	$57.93	10.791%	$64.1812	$64.18	$64.20	$64.20
Purchase #6	$88.38	4.403%	$92.2714	$92.27	$92.25	$92.30
Purchase #7	$204.78	7.567%	$220.2757	$220.28	$220.30	$220.30
7 purchase totals =	$1,013.75		$1,099.4372	$1,099.44	$1,099.50	$1,099.50