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	$93.73	11.429%	$104.4424	$104.44	$104.45	$104.40
Purchase #2	$123.31	13.162%	$139.5401	$139.54	$139.55	$139.50
Purchase #3	$248.50	6.352%	$264.2847	$264.28	$264.30	$264.30
Purchase #4	$215.56	3.399%	$222.8869	$222.89	$222.90	$222.90
Purchase #5	$96.95	8.647%	$105.3333	$105.33	$105.35	$105.30
Purchase #6	$242.41	5.564%	$255.8977	$255.90	$255.90	$255.90
Purchase #7	$73.30	13.855%	$83.4557	$83.46	$83.45	$83.50
7 purchase totals =	$1,093.76		$1,175.8408	$1,175.84	$1,175.90	$1,175.80