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	$152.48	7.564%	$164.0136	$164.01	$164.00	$164.00
Purchase #2	$42.33	10.348%	$46.7103	$46.71	$46.70	$46.70
Purchase #3	$196.31	13.732%	$223.2673	$223.27	$223.25	$223.30
Purchase #4	$64.46	8.704%	$70.0706	$70.07	$70.05	$70.10
Purchase #5	$152.40	8.837%	$165.8676	$165.87	$165.85	$165.90
Purchase #6	$186.34	7.216%	$199.7863	$199.79	$199.80	$199.80
Purchase #7	$67.94	6.681%	$72.4791	$72.48	$72.50	$72.50
7 purchase totals =	$862.26		$942.1948	$942.20	$942.15	$942.30