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	$134.93	7.557%	$145.1267	$145.13	$145.15	$145.10
Purchase #2	$81.47	9.571%	$89.2675	$89.27	$89.25	$89.30
Purchase #3	$98.61	10.677%	$109.1386	$109.14	$109.15	$109.10
Purchase #4	$184.26	8.378%	$199.6973	$199.70	$199.70	$199.70
Purchase #5	$145.46	3.364%	$150.3533	$150.35	$150.35	$150.40
Purchase #6	$80.58	9.873%	$88.5357	$88.54	$88.55	$88.50
Purchase #7	$195.88	12.494%	$220.3532	$220.35	$220.35	$220.40
7 purchase totals =	$921.19		$1,002.4723	$1,002.48	$1,002.50	$1,002.50