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	$96.67	12.868%	$109.1095	$109.11	$109.10	$109.10
Purchase #2	$41.65	6.823%	$44.4918	$44.49	$44.50	$44.50
Purchase #3	$159.83	7.305%	$171.5056	$171.51	$171.50	$171.50
Purchase #4	$198.97	3.269%	$205.4743	$205.47	$205.45	$205.50
Purchase #5	$30.92	12.196%	$34.691	$34.69	$34.70	$34.70
Purchase #6	$113.86	7.443%	$122.3346	$122.33	$122.35	$122.30
Purchase #7	$41.26	3.814%	$42.8337	$42.83	$42.85	$42.80
7 purchase totals =	$683.16		$730.4405	$730.43	$730.45	$730.40