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	$149.86	6.772%	$160.0085	$160.01	$160.00	$160.00
Purchase #2	$152.72	12.405%	$171.6649	$171.66	$171.65	$171.70
Purchase #3	$159.88	12.102%	$179.2287	$179.23	$179.25	$179.20
Purchase #4	$177.32	6.647%	$189.1065	$189.11	$189.10	$189.10
Purchase #5	$244.46	12.736%	$275.5944	$275.59	$275.60	$275.60
Purchase #6	$35.36	6.226%	$37.5615	$37.56	$37.55	$37.60
Purchase #7	$165.63	4.621%	$173.2838	$173.28	$173.30	$173.30
7 purchase totals =	$1,085.23		$1,186.4483	$1,186.44	$1,186.45	$1,186.50