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	$111.64	10.737%	$123.6268	$123.63	$123.65	$123.60
Purchase #2	$91.92	6.325%	$97.7339	$97.73	$97.75	$97.70
Purchase #3	$218.87	6.647%	$233.4183	$233.42	$233.40	$233.40
Purchase #4	$86.91	6.508%	$92.5661	$92.57	$92.55	$92.60
Purchase #5	$139.48	9.194%	$152.3038	$152.30	$152.30	$152.30
Purchase #6	$211.38	10.386%	$233.3339	$233.33	$233.35	$233.30
Purchase #7	$67.77	11.597%	$75.6293	$75.63	$75.65	$75.60
7 purchase totals =	$927.97		$1,008.6121	$1,008.61	$1,008.65	$1,008.50