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	$112.26	13.858%	$127.817	$127.82	$127.80	$127.80
Purchase #2	$79.36	7.497%	$85.3096	$85.31	$85.30	$85.30
Purchase #3	$232.28	7.832%	$250.4722	$250.47	$250.45	$250.50
Purchase #4	$130.28	12.732%	$146.8672	$146.87	$146.85	$146.90
Purchase #5	$58.66	6.669%	$62.572	$62.57	$62.55	$62.60
Purchase #6	$250.99	9.874%	$275.7728	$275.77	$275.75	$275.80
Purchase #7	$207.69	10.513%	$229.5244	$229.52	$229.50	$229.50
7 purchase totals =	$1,071.52		$1,178.3352	$1,178.33	$1,178.20	$1,178.40