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	$249.45	6.502%	$265.6692	$265.67	$265.65	$265.70
Purchase #2	$218.63	5.124%	$229.8326	$229.83	$229.85	$229.80
Purchase #3	$209.74	3.180%	$216.4097	$216.41	$216.40	$216.40
Purchase #4	$57.38	3.310%	$59.2793	$59.28	$59.30	$59.30
Purchase #5	$99.64	4.603%	$104.2264	$104.23	$104.25	$104.20
Purchase #6	$17.99	4.814%	$18.856	$18.86	$18.85	$18.90
Purchase #7	$104.49	10.834%	$115.8104	$115.81	$115.80	$115.80
7 purchase totals =	$957.32		$1,010.0836	$1,010.09	$1,010.10	$1,010.10