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	$68.62	9.525%	$75.1561	$75.16	$75.15	$75.20
Purchase #2	$98.72	12.836%	$111.3917	$111.39	$111.40	$111.40
Purchase #3	$56.70	4.667%	$59.3462	$59.35	$59.35	$59.30
Purchase #4	$54.43	5.809%	$57.5918	$57.59	$57.60	$57.60
Purchase #5	$143.44	3.457%	$148.3987	$148.40	$148.40	$148.40
Purchase #6	$57.29	7.557%	$61.6194	$61.62	$61.60	$61.60
Purchase #7	$248.81	4.817%	$260.7952	$260.80	$260.80	$260.80
7 purchase totals =	$728.01		$774.2991	$774.31	$774.30	$774.30