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	$177.54	3.121%	$183.081	$183.08	$183.10	$183.10
Purchase #2	$41.53	4.646%	$43.4595	$43.46	$43.45	$43.50
Purchase #3	$144.65	4.606%	$151.3126	$151.31	$151.30	$151.30
Purchase #4	$121.44	4.383%	$126.7627	$126.76	$126.75	$126.80
Purchase #5	$88.89	7.697%	$95.7319	$95.73	$95.75	$95.70
Purchase #6	$185.27	12.441%	$208.3194	$208.32	$208.30	$208.30
Purchase #7	$172.40	12.405%	$193.7862	$193.79	$193.80	$193.80
7 purchase totals =	$931.72		$1,002.4533	$1,002.45	$1,002.45	$1,002.50