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	$78.71	8.351%	$85.2831	$85.28	$85.30	$85.30
Purchase #2	$218.42	11.346%	$243.2019	$243.20	$243.20	$243.20
Purchase #3	$81.71	4.602%	$85.4703	$85.47	$85.45	$85.50
Purchase #4	$143.93	6.669%	$153.5287	$153.53	$153.55	$153.50
Purchase #5	$223.33	13.771%	$254.0848	$254.08	$254.10	$254.10
Purchase #6	$50.83	9.691%	$55.7559	$55.76	$55.75	$55.80
Purchase #7	$89.53	10.851%	$99.2449	$99.24	$99.25	$99.20
7 purchase totals =	$886.46		$976.5696	$976.56	$976.60	$976.60