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	$83.57	10.238%	$92.1259	$92.13	$92.15	$92.10
Purchase #2	$150.42	11.471%	$167.6747	$167.67	$167.65	$167.70
Purchase #3	$209.94	11.167%	$233.384	$233.38	$233.40	$233.40
Purchase #4	$192.55	7.279%	$206.5657	$206.57	$206.55	$206.60
Purchase #5	$90.99	11.456%	$101.4138	$101.41	$101.40	$101.40
Purchase #6	$38.48	5.580%	$40.6272	$40.63	$40.65	$40.60
Purchase #7	$226.59	10.538%	$250.4681	$250.47	$250.45	$250.50
7 purchase totals =	$992.54		$1,092.2594	$1,092.26	$1,092.25	$1,092.30