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	$131.74	8.251%	$142.6099	$142.61	$142.60	$142.60
Purchase #2	$234.82	12.607%	$264.4238	$264.42	$264.40	$264.40
Purchase #3	$142.48	5.422%	$150.2053	$150.21	$150.20	$150.20
Purchase #4	$38.74	3.151%	$39.9607	$39.96	$39.95	$40.00
Purchase #5	$187.64	3.479%	$194.168	$194.17	$194.15	$194.20
Purchase #6	$87.27	10.352%	$96.3042	$96.30	$96.30	$96.30
Purchase #7	$185.28	3.267%	$191.3331	$191.33	$191.35	$191.30
7 purchase totals =	$1,007.97		$1,079.0050	$1,079.00	$1,078.95	$1,079.00