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	$212.65	7.744%	$229.1176	$229.12	$229.10	$229.10
Purchase #2	$190.66	11.277%	$212.1607	$212.16	$212.15	$212.20
Purchase #3	$153.43	3.155%	$158.2707	$158.27	$158.25	$158.30
Purchase #4	$115.88	13.793%	$131.8633	$131.86	$131.85	$131.90
Purchase #5	$50.45	6.813%	$53.8872	$53.89	$53.90	$53.90
Purchase #6	$210.59	11.368%	$234.5299	$234.53	$234.55	$234.50
Purchase #7	$184.73	7.820%	$199.1759	$199.18	$199.20	$199.20
7 purchase totals =	$1,118.39		$1,219.0053	$1,219.01	$1,219.00	$1,219.10