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	$103.96	5.494%	$109.6716	$109.67	$109.65	$109.70
Purchase #2	$111.92	6.160%	$118.8143	$118.81	$118.80	$118.80
Purchase #3	$208.80	3.187%	$215.4545	$215.45	$215.45	$215.50
Purchase #4	$92.54	4.171%	$96.3998	$96.40	$96.40	$96.40
Purchase #5	$35.72	6.162%	$37.9211	$37.92	$37.90	$37.90
Purchase #6	$125.41	13.199%	$141.9629	$141.96	$141.95	$142.00
Purchase #7	$85.86	13.259%	$97.2442	$97.24	$97.25	$97.20
7 purchase totals =	$764.21		$817.4684	$817.45	$817.40	$817.50