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	$180.50	5.862%	$191.0809	$191.08	$191.10	$191.10
Purchase #2	$54.59	12.546%	$61.4389	$61.44	$61.45	$61.40
Purchase #3	$52.53	8.465%	$56.9767	$56.98	$57.00	$57.00
Purchase #4	$188.44	12.750%	$212.4661	$212.47	$212.45	$212.50
Purchase #5	$239.66	10.511%	$264.8507	$264.85	$264.85	$264.90
Purchase #6	$198.75	11.234%	$221.0776	$221.08	$221.10	$221.10
Purchase #7	$87.84	13.276%	$99.5016	$99.50	$99.50	$99.50
7 purchase totals =	$1,002.31		$1,107.3925	$1,107.40	$1,107.45	$1,107.50