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	$97.87	7.412%	$105.1241	$105.12	$105.10	$105.10
Purchase #2	$196.68	9.489%	$215.343	$215.34	$215.35	$215.30
Purchase #3	$65.87	10.721%	$72.9319	$72.93	$72.95	$72.90
Purchase #4	$168.63	13.790%	$191.8841	$191.88	$191.90	$191.90
Purchase #5	$220.73	9.473%	$241.6398	$241.64	$241.65	$241.60
Purchase #6	$221.72	6.480%	$236.0875	$236.09	$236.10	$236.10
Purchase #7	$46.45	7.609%	$49.9844	$49.98	$50.00	$50.00
7 purchase totals =	$1,017.95		$1,112.9948	$1,112.98	$1,113.05	$1,112.90