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	$83.68	5.180%	$88.0146	$88.01	$88.00	$88.00
Purchase #2	$20.96	4.195%	$21.8393	$21.84	$21.85	$21.80
Purchase #3	$77.60	3.467%	$80.2904	$80.29	$80.30	$80.30
Purchase #4	$12.73	7.183%	$13.6444	$13.64	$13.65	$13.60
Purchase #5	$39.27	6.276%	$41.7346	$41.73	$41.75	$41.70
Purchase #6	$72.87	11.331%	$81.1269	$81.13	$81.15	$81.10
Purchase #7	$145.86	11.242%	$162.2576	$162.26	$162.25	$162.30
7 purchase totals =	$452.97		$488.9078	$488.90	$488.95	$488.80