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	$92.86	6.511%	$98.9061	$98.91	$98.90	$98.90
Purchase #2	$237.92	7.863%	$256.6276	$256.63	$256.65	$256.60
Purchase #3	$42.40	12.404%	$47.6593	$47.66	$47.65	$47.70
Purchase #4	$183.36	7.126%	$196.4262	$196.43	$196.45	$196.40
Purchase #5	$33.59	6.586%	$35.8022	$35.80	$35.80	$35.80
Purchase #6	$248.79	11.497%	$277.3934	$277.39	$277.40	$277.40
Purchase #7	$85.46	12.414%	$96.069	$96.07	$96.05	$96.10
7 purchase totals =	$924.38		$1,008.8838	$1,008.89	$1,008.90	$1,008.90