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	$55.25	11.572%	$61.6435	$61.64	$61.65	$61.60
Purchase #2	$141.37	3.148%	$145.8203	$145.82	$145.80	$145.80
Purchase #3	$242.74	3.119%	$250.3111	$250.31	$250.30	$250.30
Purchase #4	$82.47	3.632%	$85.4653	$85.47	$85.45	$85.50
Purchase #5	$43.29	9.542%	$47.4207	$47.42	$47.40	$47.40
Purchase #6	$14.39	6.199%	$15.282	$15.28	$15.30	$15.30
Purchase #7	$188.70	12.467%	$212.2252	$212.23	$212.25	$212.20
7 purchase totals =	$768.21		$818.1681	$818.17	$818.15	$818.10