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	$91.40	7.541%	$98.2925	$98.29	$98.30	$98.30
Purchase #2	$215.33	11.664%	$240.4461	$240.45	$240.45	$240.40
Purchase #3	$59.57	8.318%	$64.525	$64.53	$64.55	$64.50
Purchase #4	$19.89	5.674%	$21.0186	$21.02	$21.00	$21.00
Purchase #5	$18.58	11.802%	$20.7728	$20.77	$20.75	$20.80
Purchase #6	$216.73	3.319%	$223.9233	$223.92	$223.90	$223.90
Purchase #7	$28.92	10.140%	$31.8525	$31.85	$31.85	$31.90
7 purchase totals =	$650.42		$700.8308	$700.83	$700.80	$700.80