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	$223.67	11.689%	$249.8148	$249.81	$249.80	$249.80
Purchase #2	$101.36	10.501%	$112.0038	$112.00	$112.00	$112.00
Purchase #3	$189.92	3.323%	$196.231	$196.23	$196.25	$196.20
Purchase #4	$47.38	6.648%	$50.5298	$50.53	$50.55	$50.50
Purchase #5	$163.25	10.539%	$180.4549	$180.45	$180.45	$180.50
Purchase #6	$113.34	10.806%	$125.5875	$125.59	$125.60	$125.60
Purchase #7	$189.41	10.720%	$209.7148	$209.71	$209.70	$209.70
7 purchase totals =	$1,028.33		$1,124.3366	$1,124.32	$1,124.35	$1,124.30