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	$142.90	6.869%	$152.7158	$152.72	$152.70	$152.70
Purchase #2	$175.95	11.802%	$196.7156	$196.72	$196.70	$196.70
Purchase #3	$235.41	3.236%	$243.0279	$243.03	$243.05	$243.00
Purchase #4	$124.87	5.269%	$131.4494	$131.45	$131.45	$131.40
Purchase #5	$136.25	11.292%	$151.6354	$151.64	$151.65	$151.60
Purchase #6	$240.97	9.307%	$263.3971	$263.40	$263.40	$263.40
Purchase #7	$25.50	11.751%	$28.4965	$28.50	$28.50	$28.50
7 purchase totals =	$1,081.85		$1,167.4377	$1,167.46	$1,167.45	$1,167.30