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	$180.88	8.430%	$196.1282	$196.13	$196.15	$196.10
Purchase #2	$152.79	5.299%	$160.8863	$160.89	$160.90	$160.90
Purchase #3	$168.83	3.738%	$175.1409	$175.14	$175.15	$175.10
Purchase #4	$59.34	3.392%	$61.3528	$61.35	$61.35	$61.40
Purchase #5	$6.35	8.481%	$6.8885	$6.89	$6.90	$6.90
Purchase #6	$220.48	8.579%	$239.395	$239.40	$239.40	$239.40
Purchase #7	$204.69	3.428%	$211.7068	$211.71	$211.70	$211.70
7 purchase totals =	$993.36		$1,051.4985	$1,051.51	$1,051.55	$1,051.50