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	$183.79	4.327%	$191.7426	$191.74	$191.75	$191.70
Purchase #2	$126.80	5.576%	$133.8704	$133.87	$133.85	$133.90
Purchase #3	$179.59	6.872%	$191.9314	$191.93	$191.95	$191.90
Purchase #4	$71.48	7.582%	$76.8996	$76.90	$76.90	$76.90
Purchase #5	$181.69	13.537%	$206.2854	$206.29	$206.30	$206.30
Purchase #6	$189.89	3.435%	$196.4127	$196.41	$196.40	$196.40
Purchase #7	$86.43	5.430%	$91.1231	$91.12	$91.10	$91.10
7 purchase totals =	$1,019.67		$1,088.2652	$1,088.26	$1,088.25	$1,088.20