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	$164.25	4.270%	$171.2635	$171.26	$171.25	$171.30
Purchase #2	$73.40	6.552%	$78.2092	$78.21	$78.20	$78.20
Purchase #3	$72.69	4.244%	$75.775	$75.78	$75.80	$75.80
Purchase #4	$246.57	7.669%	$265.4795	$265.48	$265.50	$265.50
Purchase #5	$156.64	5.830%	$165.7721	$165.77	$165.75	$165.80
Purchase #6	$25.37	10.678%	$28.079	$28.08	$28.10	$28.10
Purchase #7	$18.83	7.480%	$20.2385	$20.24	$20.25	$20.20
7 purchase totals =	$757.75		$804.8168	$804.82	$804.85	$804.90