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	$173.29	10.225%	$191.0089	$191.01	$191.00	$191.00
Purchase #2	$225.90	6.444%	$240.457	$240.46	$240.45	$240.50
Purchase #3	$98.82	9.592%	$108.2988	$108.30	$108.30	$108.30
Purchase #4	$249.50	10.269%	$275.1212	$275.12	$275.10	$275.10
Purchase #5	$173.41	10.484%	$191.5903	$191.59	$191.60	$191.60
Purchase #6	$187.80	12.760%	$211.7633	$211.76	$211.75	$211.80
Purchase #7	$36.74	13.729%	$41.784	$41.78	$41.80	$41.80
7 purchase totals =	$1,145.46		$1,260.0235	$1,260.02	$1,260.00	$1,260.10