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	$38.64	6.655%	$41.2115	$41.21	$41.20	$41.20
Purchase #2	$68.52	6.164%	$72.7436	$72.74	$72.75	$72.70
Purchase #3	$48.29	8.379%	$52.3362	$52.34	$52.35	$52.30
Purchase #4	$162.74	11.445%	$181.3656	$181.37	$181.35	$181.40
Purchase #5	$219.39	10.792%	$243.0666	$243.07	$243.05	$243.10
Purchase #6	$39.54	6.462%	$42.0951	$42.10	$42.10	$42.10
Purchase #7	$134.84	13.214%	$152.6578	$152.66	$152.65	$152.70
7 purchase totals =	$711.96		$785.4764	$785.49	$785.45	$785.50