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	$143.79	5.676%	$151.9515	$151.95	$151.95	$152.00
Purchase #2	$42.60	6.242%	$45.2591	$45.26	$45.25	$45.30
Purchase #3	$230.67	7.506%	$247.9841	$247.98	$248.00	$248.00
Purchase #4	$113.67	12.526%	$127.9083	$127.91	$127.90	$127.90
Purchase #5	$224.68	13.368%	$254.7152	$254.72	$254.70	$254.70
Purchase #6	$183.38	8.492%	$198.9526	$198.95	$198.95	$199.00
Purchase #7	$144.55	12.154%	$162.1186	$162.12	$162.10	$162.10
7 purchase totals =	$1,083.34		$1,188.8894	$1,188.89	$1,188.85	$1,189.00