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	$148.55	5.531%	$156.7663	$156.77	$156.75	$156.80
Purchase #2	$152.26	10.308%	$167.955	$167.96	$167.95	$168.00
Purchase #3	$83.96	10.520%	$92.7926	$92.79	$92.80	$92.80
Purchase #4	$110.93	10.826%	$122.9393	$122.94	$122.95	$122.90
Purchase #5	$52.55	12.571%	$59.1561	$59.16	$59.15	$59.20
Purchase #6	$89.74	10.403%	$99.0757	$99.08	$99.10	$99.10
Purchase #7	$46.56	7.258%	$49.9393	$49.94	$49.95	$49.90
7 purchase totals =	$684.55		$748.6243	$748.64	$748.65	$748.70