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	$146.80	12.714%	$165.4642	$165.46	$165.45	$165.50
Purchase #2	$6.59	13.132%	$7.4554	$7.46	$7.45	$7.50
Purchase #3	$142.41	12.812%	$160.6556	$160.66	$160.65	$160.70
Purchase #4	$233.89	11.782%	$261.4469	$261.45	$261.45	$261.40
Purchase #5	$179.91	7.869%	$194.0671	$194.07	$194.05	$194.10
Purchase #6	$52.40	6.787%	$55.9564	$55.96	$55.95	$56.00
Purchase #7	$182.36	3.294%	$188.3669	$188.37	$188.35	$188.40
7 purchase totals =	$944.36		$1,033.4125	$1,033.43	$1,033.35	$1,033.60