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	$234.79	6.825%	$250.8144	$250.81	$250.80	$250.80
Purchase #2	$151.54	11.599%	$169.1171	$169.12	$169.10	$169.10
Purchase #3	$124.91	10.123%	$137.5546	$137.55	$137.55	$137.60
Purchase #4	$61.35	10.596%	$67.8506	$67.85	$67.85	$67.90
Purchase #5	$145.59	11.350%	$162.1145	$162.11	$162.10	$162.10
Purchase #6	$136.85	4.680%	$143.2546	$143.25	$143.25	$143.30
Purchase #7	$222.30	4.255%	$231.7589	$231.76	$231.75	$231.80
7 purchase totals =	$1,077.33		$1,162.4647	$1,162.45	$1,162.40	$1,162.60