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	$224.48	3.510%	$232.3592	$232.36	$232.35	$232.40
Purchase #2	$50.62	6.410%	$53.8647	$53.86	$53.85	$53.90
Purchase #3	$239.60	6.731%	$255.7275	$255.73	$255.75	$255.70
Purchase #4	$108.34	6.529%	$115.4135	$115.41	$115.40	$115.40
Purchase #5	$91.27	10.561%	$100.909	$100.91	$100.90	$100.90
Purchase #6	$160.61	12.828%	$181.2131	$181.21	$181.20	$181.20
Purchase #7	$73.77	5.654%	$77.941	$77.94	$77.95	$77.90
7 purchase totals =	$948.69		$1,017.4280	$1,017.42	$1,017.40	$1,017.40