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	$188.27	4.496%	$196.7346	$196.73	$196.75	$196.70
Purchase #2	$55.85	4.355%	$58.2823	$58.28	$58.30	$58.30
Purchase #3	$122.63	4.849%	$128.5763	$128.58	$128.60	$128.60
Purchase #4	$163.63	9.404%	$179.0178	$179.02	$179.00	$179.00
Purchase #5	$233.88	3.661%	$242.4423	$242.44	$242.45	$242.40
Purchase #6	$71.30	9.579%	$78.1298	$78.13	$78.15	$78.10
Purchase #7	$98.44	13.554%	$111.7826	$111.78	$111.80	$111.80
7 purchase totals =	$934.00		$994.9657	$994.96	$995.05	$994.90