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	$165.73	7.557%	$178.2542	$178.25	$178.25	$178.30
Purchase #2	$95.58	5.606%	$100.9382	$100.94	$100.95	$100.90
Purchase #3	$237.84	5.491%	$250.8998	$250.90	$250.90	$250.90
Purchase #4	$179.76	8.136%	$194.3853	$194.39	$194.40	$194.40
Purchase #5	$225.79	5.199%	$237.5288	$237.53	$237.55	$237.50
Purchase #6	$33.60	5.418%	$35.4204	$35.42	$35.40	$35.40
Purchase #7	$168.65	3.702%	$174.8934	$174.89	$174.90	$174.90
7 purchase totals =	$1,106.95		$1,172.3201	$1,172.32	$1,172.35	$1,172.30