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	$79.42	3.595%	$82.2751	$82.28	$82.30	$82.30
Purchase #2	$141.31	12.193%	$158.5399	$158.54	$158.55	$158.50
Purchase #3	$112.74	8.827%	$122.6916	$122.69	$122.70	$122.70
Purchase #4	$247.38	8.627%	$268.7215	$268.72	$268.70	$268.70
Purchase #5	$72.95	8.191%	$78.9253	$78.93	$78.95	$78.90
Purchase #6	$218.96	4.705%	$229.2621	$229.26	$229.25	$229.30
Purchase #7	$101.75	9.196%	$111.1069	$111.11	$111.10	$111.10
7 purchase totals =	$974.51		$1,051.5224	$1,051.53	$1,051.55	$1,051.50