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	$104.78	13.540%	$118.9672	$118.97	$118.95	$119.00
Purchase #2	$99.61	5.737%	$105.3246	$105.32	$105.30	$105.30
Purchase #3	$211.56	13.459%	$240.0339	$240.03	$240.05	$240.00
Purchase #4	$149.31	11.569%	$166.5837	$166.58	$166.60	$166.60
Purchase #5	$97.44	11.762%	$108.9009	$108.90	$108.90	$108.90
Purchase #6	$216.49	6.434%	$230.419	$230.42	$230.40	$230.40
Purchase #7	$73.48	6.708%	$78.409	$78.41	$78.40	$78.40
7 purchase totals =	$952.67		$1,048.6383	$1,048.63	$1,048.60	$1,048.60