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	$195.93	4.310%	$204.3746	$204.37	$204.35	$204.40
Purchase #2	$81.55	11.461%	$90.8964	$90.90	$90.90	$90.90
Purchase #3	$61.69	13.119%	$69.7831	$69.78	$69.80	$69.80
Purchase #4	$71.64	9.279%	$78.2875	$78.29	$78.30	$78.30
Purchase #5	$11.27	9.366%	$12.3255	$12.33	$12.35	$12.30
Purchase #6	$152.61	4.774%	$159.8956	$159.90	$159.90	$159.90
Purchase #7	$223.52	9.556%	$244.8796	$244.88	$244.90	$244.90
7 purchase totals =	$798.21		$860.4423	$860.45	$860.50	$860.50