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	$218.72	10.796%	$242.333	$242.33	$242.35	$242.30
Purchase #2	$76.39	7.698%	$82.2705	$82.27	$82.25	$82.30
Purchase #3	$210.86	5.579%	$222.6239	$222.62	$222.60	$222.60
Purchase #4	$130.68	4.658%	$136.7671	$136.77	$136.75	$136.80
Purchase #5	$227.54	9.114%	$248.278	$248.28	$248.30	$248.30
Purchase #6	$158.31	7.134%	$169.6038	$169.60	$169.60	$169.60
Purchase #7	$153.36	9.645%	$168.1516	$168.15	$168.15	$168.20
7 purchase totals =	$1,175.86		$1,270.0279	$1,270.02	$1,270.00	$1,270.10