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	$148.28	9.373%	$162.1783	$162.18	$162.20	$162.20
Purchase #2	$57.95	7.465%	$62.276	$62.28	$62.30	$62.30
Purchase #3	$244.54	4.330%	$255.1286	$255.13	$255.15	$255.10
Purchase #4	$118.69	10.424%	$131.0622	$131.06	$131.05	$131.10
Purchase #5	$153.59	9.397%	$168.0229	$168.02	$168.00	$168.00
Purchase #6	$139.73	5.167%	$146.9498	$146.95	$146.95	$146.90
Purchase #7	$223.96	12.208%	$251.301	$251.30	$251.30	$251.30
7 purchase totals =	$1,086.74		$1,176.9188	$1,176.92	$1,176.95	$1,176.90