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	$141.93	4.258%	$147.9734	$147.97	$147.95	$148.00
Purchase #2	$86.48	11.306%	$96.2574	$96.26	$96.25	$96.30
Purchase #3	$63.93	10.612%	$70.7143	$70.71	$70.70	$70.70
Purchase #4	$91.95	12.508%	$103.4511	$103.45	$103.45	$103.50
Purchase #5	$118.50	13.188%	$134.1278	$134.13	$134.15	$134.10
Purchase #6	$111.61	13.808%	$127.0211	$127.02	$127.00	$127.00
Purchase #7	$51.29	4.187%	$53.4375	$53.44	$53.45	$53.40
7 purchase totals =	$665.69		$732.9826	$732.98	$732.95	$733.00