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	$52.84	12.199%	$59.286	$59.29	$59.30	$59.30
Purchase #2	$152.54	8.622%	$165.692	$165.69	$165.70	$165.70
Purchase #3	$81.95	9.685%	$89.8869	$89.89	$89.90	$89.90
Purchase #4	$86.97	12.800%	$98.1022	$98.10	$98.10	$98.10
Purchase #5	$236.26	3.707%	$245.0182	$245.02	$245.00	$245.00
Purchase #6	$42.94	4.805%	$45.0033	$45.00	$45.00	$45.00
Purchase #7	$142.82	5.413%	$150.5508	$150.55	$150.55	$150.60
7 purchase totals =	$796.32		$853.5394	$853.54	$853.55	$853.60