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	$100.88	8.114%	$109.0654	$109.07	$109.05	$109.10
Purchase #2	$69.72	13.102%	$78.8547	$78.85	$78.85	$78.90
Purchase #3	$242.66	12.514%	$273.0265	$273.03	$273.05	$273.00
Purchase #4	$182.28	3.612%	$188.864	$188.86	$188.85	$188.90
Purchase #5	$182.25	12.178%	$204.4444	$204.44	$204.45	$204.40
Purchase #6	$172.72	3.676%	$179.0692	$179.07	$179.05	$179.10
Purchase #7	$184.95	6.503%	$196.9773	$196.98	$197.00	$197.00
7 purchase totals =	$1,135.46		$1,230.3015	$1,230.30	$1,230.30	$1,230.40