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	$191.70	4.554%	$200.43	$200.43	$200.45	$200.40
Purchase #2	$211.66	3.133%	$218.2913	$218.29	$218.30	$218.30
Purchase #3	$168.79	12.301%	$189.5529	$189.55	$189.55	$189.60
Purchase #4	$159.27	10.211%	$175.5331	$175.53	$175.55	$175.50
Purchase #5	$149.48	11.809%	$167.1321	$167.13	$167.15	$167.10
Purchase #6	$110.66	12.401%	$124.3829	$124.38	$124.40	$124.40
Purchase #7	$218.36	3.455%	$225.9043	$225.90	$225.90	$225.90
7 purchase totals =	$1,209.92		$1,301.2266	$1,301.21	$1,301.30	$1,301.20