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	$187.37	9.819%	$205.7679	$205.77	$205.75	$205.80
Purchase #2	$106.33	5.554%	$112.2356	$112.24	$112.25	$112.20
Purchase #3	$169.61	5.487%	$178.9165	$178.92	$178.90	$178.90
Purchase #4	$176.53	5.304%	$185.8932	$185.89	$185.90	$185.90
Purchase #5	$71.39	6.829%	$76.2652	$76.27	$76.25	$76.30
Purchase #6	$11.71	7.504%	$12.5887	$12.59	$12.60	$12.60
Purchase #7	$18.75	10.197%	$20.6619	$20.66	$20.65	$20.70
7 purchase totals =	$741.69		$792.3290	$792.34	$792.30	$792.40