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	$185.59	11.536%	$206.9997	$207.00	$207.00	$207.00
Purchase #2	$51.29	7.872%	$55.3275	$55.33	$55.35	$55.30
Purchase #3	$143.49	10.478%	$158.5249	$158.52	$158.50	$158.50
Purchase #4	$176.95	11.148%	$196.6764	$196.68	$196.70	$196.70
Purchase #5	$70.91	5.222%	$74.6129	$74.61	$74.60	$74.60
Purchase #6	$81.69	9.629%	$89.5559	$89.56	$89.55	$89.60
Purchase #7	$236.63	4.625%	$247.5741	$247.57	$247.55	$247.60
7 purchase totals =	$946.55		$1,029.2714	$1,029.27	$1,029.25	$1,029.30