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	$173.62	4.412%	$181.2801	$181.28	$181.30	$181.30
Purchase #2	$170.77	10.629%	$188.9211	$188.92	$188.90	$188.90
Purchase #3	$91.74	10.637%	$101.4984	$101.50	$101.50	$101.50
Purchase #4	$127.66	12.452%	$143.5562	$143.56	$143.55	$143.60
Purchase #5	$160.48	13.180%	$181.6313	$181.63	$181.65	$181.60
Purchase #6	$58.89	6.859%	$62.9293	$62.93	$62.95	$62.90
Purchase #7	$183.53	3.548%	$190.0416	$190.04	$190.05	$190.00
7 purchase totals =	$966.69		$1,049.8580	$1,049.86	$1,049.90	$1,049.80