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	$54.25	10.223%	$59.796	$59.80	$59.80	$59.80
Purchase #2	$123.41	4.302%	$128.7191	$128.72	$128.70	$128.70
Purchase #3	$105.62	3.399%	$109.21	$109.21	$109.20	$109.20
Purchase #4	$223.65	6.355%	$237.863	$237.86	$237.85	$237.90
Purchase #5	$245.73	12.742%	$277.0409	$277.04	$277.05	$277.00
Purchase #6	$60.35	11.149%	$67.0784	$67.08	$67.10	$67.10
Purchase #7	$160.78	7.445%	$172.7501	$172.75	$172.75	$172.80
7 purchase totals =	$973.79		$1,052.4575	$1,052.46	$1,052.45	$1,052.50