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	$91.38	12.482%	$102.7861	$102.79	$102.80	$102.80
Purchase #2	$55.32	7.469%	$59.4519	$59.45	$59.45	$59.50
Purchase #3	$233.67	9.616%	$256.1397	$256.14	$256.15	$256.10
Purchase #4	$223.56	5.861%	$236.6629	$236.66	$236.65	$236.70
Purchase #5	$227.91	9.613%	$249.819	$249.82	$249.80	$249.80
Purchase #6	$148.85	5.209%	$156.6036	$156.60	$156.60	$156.60
Purchase #7	$91.44	9.383%	$100.0198	$100.02	$100.00	$100.00
7 purchase totals =	$1,072.13		$1,161.4830	$1,161.48	$1,161.45	$1,161.50