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	$211.32	8.111%	$228.4602	$228.46	$228.45	$228.50
Purchase #2	$126.33	3.427%	$130.6593	$130.66	$130.65	$130.70
Purchase #3	$144.71	12.510%	$162.8132	$162.81	$162.80	$162.80
Purchase #4	$82.56	8.681%	$89.727	$89.73	$89.75	$89.70
Purchase #5	$106.85	5.240%	$112.4489	$112.45	$112.45	$112.40
Purchase #6	$188.89	12.842%	$213.1473	$213.15	$213.15	$213.10
Purchase #7	$207.74	8.418%	$225.2276	$225.23	$225.25	$225.20
7 purchase totals =	$1,068.40		$1,162.4835	$1,162.49	$1,162.50	$1,162.40