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	$94.89	7.210%	$101.7316	$101.73	$101.75	$101.70
Purchase #2	$28.66	11.585%	$31.9803	$31.98	$32.00	$32.00
Purchase #3	$127.38	8.199%	$137.8239	$137.82	$137.80	$137.80
Purchase #4	$122.82	8.702%	$133.5078	$133.51	$133.50	$133.50
Purchase #5	$219.46	4.505%	$229.3467	$229.35	$229.35	$229.30
Purchase #6	$221.96	12.693%	$250.1334	$250.13	$250.15	$250.10
Purchase #7	$41.27	3.190%	$42.5865	$42.59	$42.60	$42.60
7 purchase totals =	$856.44		$927.1102	$927.11	$927.15	$927.00