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	$225.85	8.519%	$245.0902	$245.09	$245.10	$245.10
Purchase #2	$141.93	13.348%	$160.8748	$160.87	$160.85	$160.90
Purchase #3	$70.34	3.740%	$72.9707	$72.97	$72.95	$73.00
Purchase #4	$63.59	9.556%	$69.6667	$69.67	$69.65	$69.70
Purchase #5	$150.74	11.405%	$167.9319	$167.93	$167.95	$167.90
Purchase #6	$176.38	11.568%	$196.7836	$196.78	$196.80	$196.80
Purchase #7	$173.57	4.415%	$181.2331	$181.23	$181.25	$181.20
7 purchase totals =	$1,002.40		$1,094.5510	$1,094.54	$1,094.55	$1,094.60