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	$43.93	3.487%	$45.4618	$45.46	$45.45	$45.50
Purchase #2	$138.69	10.647%	$153.4563	$153.46	$153.45	$153.50
Purchase #3	$245.25	9.419%	$268.3501	$268.35	$268.35	$268.40
Purchase #4	$110.82	12.502%	$124.6747	$124.67	$124.65	$124.70
Purchase #5	$142.54	5.408%	$150.2486	$150.25	$150.25	$150.20
Purchase #6	$213.85	12.170%	$239.8755	$239.88	$239.90	$239.90
Purchase #7	$168.51	11.856%	$188.4885	$188.49	$188.50	$188.50
7 purchase totals =	$1,063.59		$1,170.5555	$1,170.56	$1,170.55	$1,170.70