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	$175.75	7.236%	$188.4673	$188.47	$188.45	$188.50
Purchase #2	$101.54	12.123%	$113.8497	$113.85	$113.85	$113.80
Purchase #3	$209.39	4.730%	$219.2941	$219.29	$219.30	$219.30
Purchase #4	$171.60	4.664%	$179.6034	$179.60	$179.60	$179.60
Purchase #5	$181.85	3.809%	$188.7767	$188.78	$188.80	$188.80
Purchase #6	$119.82	6.174%	$127.2177	$127.22	$127.20	$127.20
Purchase #7	$247.91	6.191%	$263.2581	$263.26	$263.25	$263.30
7 purchase totals =	$1,207.86		$1,280.4670	$1,280.47	$1,280.45	$1,280.50