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	$135.42	11.427%	$150.8944	$150.89	$150.90	$150.90
Purchase #2	$131.69	11.592%	$146.9555	$146.96	$146.95	$147.00
Purchase #3	$123.74	12.578%	$139.304	$139.30	$139.30	$139.30
Purchase #4	$242.74	6.556%	$258.654	$258.65	$258.65	$258.70
Purchase #5	$234.41	3.149%	$241.7916	$241.79	$241.80	$241.80
Purchase #6	$91.94	4.705%	$96.2658	$96.27	$96.25	$96.30
Purchase #7	$57.87	4.225%	$60.315	$60.32	$60.30	$60.30
7 purchase totals =	$1,017.81		$1,094.1803	$1,094.18	$1,094.15	$1,094.30