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	$166.73	10.444%	$184.1433	$184.14	$184.15	$184.10
Purchase #2	$47.65	11.300%	$53.0345	$53.03	$53.05	$53.00
Purchase #3	$55.66	10.165%	$61.3178	$61.32	$61.30	$61.30
Purchase #4	$57.28	4.154%	$59.6594	$59.66	$59.65	$59.70
Purchase #5	$59.47	12.720%	$67.0346	$67.03	$67.05	$67.00
Purchase #6	$203.58	11.862%	$227.7287	$227.73	$227.75	$227.70
Purchase #7	$104.49	7.371%	$112.192	$112.19	$112.20	$112.20
7 purchase totals =	$694.86		$765.1103	$765.10	$765.15	$765.00