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	$240.89	9.251%	$263.1747	$263.17	$263.15	$263.20
Purchase #2	$60.35	9.216%	$65.9119	$65.91	$65.90	$65.90
Purchase #3	$242.38	8.758%	$263.6076	$263.61	$263.60	$263.60
Purchase #4	$61.40	9.180%	$67.0365	$67.04	$67.05	$67.00
Purchase #5	$192.71	13.682%	$219.0766	$219.08	$219.10	$219.10
Purchase #6	$78.41	5.814%	$82.9688	$82.97	$82.95	$83.00
Purchase #7	$170.82	5.658%	$180.485	$180.49	$180.50	$180.50
7 purchase totals =	$1,046.96		$1,142.2611	$1,142.27	$1,142.25	$1,142.30