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	$165.98	9.511%	$181.7664	$181.77	$181.75	$181.80
Purchase #2	$40.56	5.746%	$42.8906	$42.89	$42.90	$42.90
Purchase #3	$214.85	6.288%	$228.3598	$228.36	$228.35	$228.40
Purchase #4	$222.75	9.283%	$243.4279	$243.43	$243.45	$243.40
Purchase #5	$187.27	9.654%	$205.349	$205.35	$205.35	$205.30
Purchase #6	$244.34	12.661%	$275.2759	$275.28	$275.30	$275.30
Purchase #7	$153.71	11.630%	$171.5865	$171.59	$171.60	$171.60
7 purchase totals =	$1,229.46		$1,348.6561	$1,348.67	$1,348.70	$1,348.70