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	$205.27	11.446%	$228.7652	$228.77	$228.75	$228.80
Purchase #2	$124.72	11.727%	$139.3459	$139.35	$139.35	$139.30
Purchase #3	$244.87	3.386%	$253.1613	$253.16	$253.15	$253.20
Purchase #4	$68.79	13.380%	$77.9941	$77.99	$78.00	$78.00
Purchase #5	$51.53	7.250%	$55.2659	$55.27	$55.25	$55.30
Purchase #6	$82.80	8.372%	$89.732	$89.73	$89.75	$89.70
Purchase #7	$147.58	12.767%	$166.4215	$166.42	$166.40	$166.40
7 purchase totals =	$925.56		$1,010.6859	$1,010.69	$1,010.65	$1,010.70