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	$165.50	8.209%	$179.0859	$179.09	$179.10	$179.10
Purchase #2	$180.47	7.193%	$193.4512	$193.45	$193.45	$193.50
Purchase #3	$219.68	9.315%	$240.1432	$240.14	$240.15	$240.10
Purchase #4	$196.50	11.480%	$219.0582	$219.06	$219.05	$219.10
Purchase #5	$104.62	4.819%	$109.6616	$109.66	$109.65	$109.70
Purchase #6	$144.31	4.332%	$150.5615	$150.56	$150.55	$150.60
Purchase #7	$92.81	6.769%	$99.0923	$99.09	$99.10	$99.10
7 purchase totals =	$1,103.89		$1,191.0539	$1,191.05	$1,191.05	$1,191.20