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	$85.51	6.613%	$91.1648	$91.16	$91.15	$91.20
Purchase #2	$17.74	9.662%	$19.454	$19.45	$19.45	$19.50
Purchase #3	$154.54	5.152%	$162.5019	$162.50	$162.50	$162.50
Purchase #4	$157.73	12.481%	$177.4163	$177.42	$177.40	$177.40
Purchase #5	$168.91	9.845%	$185.5392	$185.54	$185.55	$185.50
Purchase #6	$154.83	6.433%	$164.7902	$164.79	$164.80	$164.80
Purchase #7	$156.85	6.774%	$167.475	$167.48	$167.50	$167.50
7 purchase totals =	$896.11		$968.3414	$968.34	$968.35	$968.40