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	$123.54	3.370%	$127.7033	$127.70	$127.70	$127.70
Purchase #2	$88.34	3.801%	$91.6978	$91.70	$91.70	$91.70
Purchase #3	$67.65	6.637%	$72.1399	$72.14	$72.15	$72.10
Purchase #4	$152.39	3.804%	$158.1869	$158.19	$158.20	$158.20
Purchase #5	$159.66	5.172%	$167.9176	$167.92	$167.90	$167.90
Purchase #6	$98.75	12.582%	$111.1747	$111.17	$111.15	$111.20
Purchase #7	$151.87	3.372%	$156.9911	$156.99	$157.00	$157.00
7 purchase totals =	$842.20		$885.8113	$885.81	$885.80	$885.80