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	$156.36	12.769%	$176.3256	$176.33	$176.35	$176.30
Purchase #2	$74.88	12.103%	$83.9427	$83.94	$83.95	$83.90
Purchase #3	$109.28	4.726%	$114.4446	$114.44	$114.45	$114.40
Purchase #4	$40.67	3.258%	$41.995	$42.00	$42.00	$42.00
Purchase #5	$144.89	11.864%	$162.0797	$162.08	$162.10	$162.10
Purchase #6	$223.90	11.616%	$249.9082	$249.91	$249.90	$249.90
Purchase #7	$250.54	5.201%	$263.5706	$263.57	$263.55	$263.60
7 purchase totals =	$1,000.52		$1,092.2664	$1,092.27	$1,092.30	$1,092.20