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	$106.91	4.490%	$111.7103	$111.71	$111.70	$111.70
Purchase #2	$226.38	13.645%	$257.2696	$257.27	$257.25	$257.30
Purchase #3	$161.50	4.851%	$169.3344	$169.33	$169.35	$169.30
Purchase #4	$72.84	8.121%	$78.7553	$78.76	$78.75	$78.80
Purchase #5	$39.98	13.228%	$45.2686	$45.27	$45.25	$45.30
Purchase #6	$165.40	5.532%	$174.5499	$174.55	$174.55	$174.50
Purchase #7	$189.64	13.227%	$214.7237	$214.72	$214.70	$214.70
7 purchase totals =	$962.65		$1,051.6118	$1,051.61	$1,051.55	$1,051.60