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	$116.78	7.121%	$125.0959	$125.10	$125.10	$125.10
Purchase #2	$29.53	9.123%	$32.224	$32.22	$32.20	$32.20
Purchase #3	$108.89	12.607%	$122.6178	$122.62	$122.60	$122.60
Purchase #4	$91.63	9.841%	$100.6473	$100.65	$100.65	$100.60
Purchase #5	$52.91	12.279%	$59.4068	$59.41	$59.40	$59.40
Purchase #6	$170.76	8.370%	$185.0526	$185.05	$185.05	$185.10
Purchase #7	$195.27	12.505%	$219.6885	$219.69	$219.70	$219.70
7 purchase totals =	$765.77		$844.7329	$844.74	$844.70	$844.70