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	$94.55	4.558%	$98.8596	$98.86	$98.85	$98.90
Purchase #2	$46.26	9.194%	$50.5131	$50.51	$50.50	$50.50
Purchase #3	$57.81	3.580%	$59.8796	$59.88	$59.90	$59.90
Purchase #4	$180.27	4.490%	$188.3641	$188.36	$188.35	$188.40
Purchase #5	$56.71	4.448%	$59.2325	$59.23	$59.25	$59.20
Purchase #6	$141.47	4.152%	$147.3438	$147.34	$147.35	$147.30
Purchase #7	$140.81	6.773%	$150.3471	$150.35	$150.35	$150.30
7 purchase totals =	$717.88		$754.5398	$754.53	$754.55	$754.50