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	$152.64	4.862%	$160.0614	$160.06	$160.05	$160.10
Purchase #2	$27.58	4.251%	$28.7524	$28.75	$28.75	$28.80
Purchase #3	$188.93	3.109%	$194.8038	$194.80	$194.80	$194.80
Purchase #4	$86.32	11.476%	$96.2261	$96.23	$96.25	$96.20
Purchase #5	$239.28	6.586%	$255.039	$255.04	$255.05	$255.00
Purchase #6	$130.70	12.578%	$147.1394	$147.14	$147.15	$147.10
Purchase #7	$65.56	3.554%	$67.89	$67.89	$67.90	$67.90
7 purchase totals =	$891.01		$949.9121	$949.91	$949.95	$949.90