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	$186.77	3.510%	$193.3256	$193.33	$193.35	$193.30
Purchase #2	$214.72	6.627%	$228.9495	$228.95	$228.95	$228.90
Purchase #3	$123.48	6.529%	$131.542	$131.54	$131.55	$131.50
Purchase #4	$184.50	7.263%	$197.9002	$197.90	$197.90	$197.90
Purchase #5	$25.41	5.530%	$26.8152	$26.82	$26.80	$26.80
Purchase #6	$228.39	9.710%	$250.5667	$250.57	$250.55	$250.60
Purchase #7	$67.80	5.327%	$71.4117	$71.41	$71.40	$71.40
7 purchase totals =	$1,031.07		$1,100.5109	$1,100.52	$1,100.50	$1,100.40