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	$81.69	8.697%	$88.7946	$88.79	$88.80	$88.80
Purchase #2	$67.37	3.719%	$69.8755	$69.88	$69.90	$69.90
Purchase #3	$105.43	13.322%	$119.4754	$119.48	$119.50	$119.50
Purchase #4	$144.41	4.152%	$150.4059	$150.41	$150.40	$150.40
Purchase #5	$201.96	3.612%	$209.2548	$209.25	$209.25	$209.30
Purchase #6	$133.96	6.256%	$142.3405	$142.34	$142.35	$142.30
Purchase #7	$244.97	3.874%	$254.4601	$254.46	$254.45	$254.50
7 purchase totals =	$979.79		$1,034.6068	$1,034.61	$1,034.65	$1,034.70