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	$98.34	13.354%	$111.4723	$111.47	$111.45	$111.50
Purchase #2	$189.87	3.719%	$196.9313	$196.93	$196.95	$196.90
Purchase #3	$207.66	10.323%	$229.0967	$229.10	$229.10	$229.10
Purchase #4	$19.56	4.777%	$20.4944	$20.49	$20.50	$20.50
Purchase #5	$164.50	11.396%	$183.2464	$183.25	$183.25	$183.20
Purchase #6	$223.46	12.250%	$250.8339	$250.83	$250.85	$250.80
Purchase #7	$96.85	13.308%	$109.7388	$109.74	$109.75	$109.70
7 purchase totals =	$1,000.24		$1,101.8138	$1,101.81	$1,101.85	$1,101.70