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	$106.64	7.697%	$114.8481	$114.85	$114.85	$114.80
Purchase #2	$222.87	8.835%	$242.5606	$242.56	$242.55	$242.60
Purchase #3	$162.63	5.695%	$171.8918	$171.89	$171.90	$171.90
Purchase #4	$72.92	5.190%	$76.7045	$76.70	$76.70	$76.70
Purchase #5	$184.75	5.296%	$194.5344	$194.53	$194.55	$194.50
Purchase #6	$240.94	13.848%	$274.3054	$274.31	$274.30	$274.30
Purchase #7	$90.71	11.112%	$100.7897	$100.79	$100.80	$100.80
7 purchase totals =	$1,081.46		$1,175.6345	$1,175.63	$1,175.65	$1,175.60