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	$62.27	11.696%	$69.5531	$69.55	$69.55	$69.60
Purchase #2	$92.48	10.157%	$101.8732	$101.87	$101.85	$101.90
Purchase #3	$114.59	12.512%	$128.9275	$128.93	$128.95	$128.90
Purchase #4	$58.25	6.656%	$62.1271	$62.13	$62.15	$62.10
Purchase #5	$53.25	7.646%	$57.3215	$57.32	$57.30	$57.30
Purchase #6	$100.28	11.290%	$111.6016	$111.60	$111.60	$111.60
Purchase #7	$60.39	6.137%	$64.0961	$64.10	$64.10	$64.10
7 purchase totals =	$541.51		$595.5001	$595.50	$595.50	$595.50