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	$77.75	10.353%	$85.7995	$85.80	$85.80	$85.80
Purchase #2	$238.53	10.805%	$264.3032	$264.30	$264.30	$264.30
Purchase #3	$43.94	4.121%	$45.7508	$45.75	$45.75	$45.80
Purchase #4	$12.25	11.231%	$13.6258	$13.63	$13.65	$13.60
Purchase #5	$84.25	7.620%	$90.6699	$90.67	$90.65	$90.70
Purchase #6	$28.83	12.815%	$32.5246	$32.52	$32.50	$32.50
Purchase #7	$188.79	11.745%	$210.9634	$210.96	$210.95	$211.00
7 purchase totals =	$674.34		$743.6372	$743.63	$743.60	$743.70