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	$171.76	11.745%	$191.9332	$191.93	$191.95	$191.90
Purchase #2	$83.42	13.836%	$94.962	$94.96	$94.95	$95.00
Purchase #3	$114.50	8.466%	$124.1936	$124.19	$124.20	$124.20
Purchase #4	$42.35	8.454%	$45.9303	$45.93	$45.95	$45.90
Purchase #5	$115.79	6.496%	$123.3117	$123.31	$123.30	$123.30
Purchase #6	$39.56	5.120%	$41.5855	$41.59	$41.60	$41.60
Purchase #7	$221.35	3.448%	$228.9821	$228.98	$229.00	$229.00
7 purchase totals =	$788.73		$850.8984	$850.89	$850.95	$850.90