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	$118.52	5.810%	$125.406	$125.41	$125.40	$125.40
Purchase #2	$81.27	10.155%	$89.523	$89.52	$89.50	$89.50
Purchase #3	$169.81	6.153%	$180.2584	$180.26	$180.25	$180.30
Purchase #4	$116.52	9.666%	$127.7828	$127.78	$127.80	$127.80
Purchase #5	$120.42	7.608%	$129.5816	$129.58	$129.60	$129.60
Purchase #6	$83.87	12.267%	$94.1583	$94.16	$94.15	$94.20
Purchase #7	$82.36	12.674%	$92.7983	$92.80	$92.80	$92.80
7 purchase totals =	$772.77		$839.5084	$839.51	$839.50	$839.60