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	$197.48	6.156%	$209.6369	$209.64	$209.65	$209.60
Purchase #2	$128.41	7.425%	$137.9444	$137.94	$137.95	$137.90
Purchase #3	$114.32	8.366%	$123.884	$123.88	$123.90	$123.90
Purchase #4	$32.70	3.142%	$33.7274	$33.73	$33.75	$33.70
Purchase #5	$212.39	4.869%	$222.7313	$222.73	$222.75	$222.70
Purchase #6	$183.92	11.612%	$205.2768	$205.28	$205.30	$205.30
Purchase #7	$54.60	5.568%	$57.6401	$57.64	$57.65	$57.60
7 purchase totals =	$923.82		$990.8409	$990.84	$990.95	$990.70