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	$226.30	10.711%	$250.539	$250.54	$250.55	$250.50
Purchase #2	$156.74	9.555%	$171.7165	$171.72	$171.70	$171.70
Purchase #3	$198.78	5.704%	$210.1184	$210.12	$210.10	$210.10
Purchase #4	$215.33	3.136%	$222.0827	$222.08	$222.10	$222.10
Purchase #5	$99.51	13.501%	$112.9448	$112.94	$112.95	$112.90
Purchase #6	$169.80	3.578%	$175.8754	$175.88	$175.90	$175.90
Purchase #7	$9.55	12.177%	$10.7129	$10.71	$10.70	$10.70
7 purchase totals =	$1,076.01		$1,153.9897	$1,153.99	$1,154.00	$1,153.90