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	$220.39	11.212%	$245.1001	$245.10	$245.10	$245.10
Purchase #2	$85.44	13.427%	$96.912	$96.91	$96.90	$96.90
Purchase #3	$181.54	10.323%	$200.2804	$200.28	$200.30	$200.30
Purchase #4	$39.78	5.309%	$41.8919	$41.89	$41.90	$41.90
Purchase #5	$34.40	8.377%	$37.2817	$37.28	$37.30	$37.30
Purchase #6	$114.91	3.252%	$118.6469	$118.65	$118.65	$118.60
Purchase #7	$55.30	12.650%	$62.2955	$62.30	$62.30	$62.30
7 purchase totals =	$731.76		$802.4085	$802.41	$802.45	$802.40