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	$98.31	11.123%	$109.245	$109.25	$109.25	$109.20
Purchase #2	$152.70	10.572%	$168.8434	$168.84	$168.85	$168.80
Purchase #3	$46.50	7.248%	$49.8703	$49.87	$49.85	$49.90
Purchase #4	$205.59	7.689%	$221.3978	$221.40	$221.40	$221.40
Purchase #5	$125.83	3.444%	$130.1636	$130.16	$130.15	$130.20
Purchase #6	$51.45	9.602%	$56.3902	$56.39	$56.40	$56.40
Purchase #7	$41.51	9.269%	$45.3576	$45.36	$45.35	$45.40
7 purchase totals =	$721.89		$781.2679	$781.27	$781.25	$781.30