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	$212.36	5.374%	$223.7722	$223.77	$223.75	$223.80
Purchase #2	$52.85	11.634%	$58.9986	$59.00	$59.00	$59.00
Purchase #3	$65.25	3.871%	$67.7758	$67.78	$67.80	$67.80
Purchase #4	$173.63	4.290%	$181.0787	$181.08	$181.10	$181.10
Purchase #5	$179.35	3.309%	$185.2847	$185.28	$185.30	$185.30
Purchase #6	$220.85	12.487%	$248.4275	$248.43	$248.45	$248.40
Purchase #7	$181.58	7.308%	$194.8499	$194.85	$194.85	$194.80
7 purchase totals =	$1,085.87		$1,160.1874	$1,160.19	$1,160.25	$1,160.20