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	$62.73	5.737%	$66.3288	$66.33	$66.35	$66.30
Purchase #2	$101.35	7.782%	$109.2371	$109.24	$109.25	$109.20
Purchase #3	$100.39	9.219%	$109.645	$109.65	$109.65	$109.60
Purchase #4	$158.72	6.746%	$169.4273	$169.43	$169.45	$169.40
Purchase #5	$25.71	10.669%	$28.453	$28.45	$28.45	$28.50
Purchase #6	$145.87	6.327%	$155.0992	$155.10	$155.10	$155.10
Purchase #7	$55.92	7.125%	$59.9043	$59.90	$59.90	$59.90
7 purchase totals =	$650.69		$698.0947	$698.10	$698.15	$698.00