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	$85.32	5.257%	$89.8053	$89.81	$89.80	$89.80
Purchase #2	$152.95	6.474%	$162.852	$162.85	$162.85	$162.90
Purchase #3	$33.25	5.533%	$35.0897	$35.09	$35.10	$35.10
Purchase #4	$170.76	7.610%	$183.7548	$183.75	$183.75	$183.80
Purchase #5	$11.51	4.226%	$11.9964	$12.00	$12.00	$12.00
Purchase #6	$155.85	8.639%	$169.3139	$169.31	$169.30	$169.30
Purchase #7	$84.39	7.521%	$90.737	$90.74	$90.75	$90.70
7 purchase totals =	$694.03		$743.5491	$743.55	$743.55	$743.60