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	$188.98	7.807%	$203.7337	$203.73	$203.75	$203.70
Purchase #2	$189.50	5.722%	$200.3432	$200.34	$200.35	$200.30
Purchase #3	$73.69	7.140%	$78.9515	$78.95	$78.95	$79.00
Purchase #4	$152.42	10.380%	$168.2412	$168.24	$168.25	$168.20
Purchase #5	$248.54	10.762%	$275.2879	$275.29	$275.30	$275.30
Purchase #6	$61.44	8.278%	$66.526	$66.53	$66.55	$66.50
Purchase #7	$123.88	6.107%	$131.4454	$131.45	$131.45	$131.40
7 purchase totals =	$1,038.45		$1,124.5289	$1,124.53	$1,124.60	$1,124.40