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	$180.31	5.174%	$189.6392	$189.64	$189.65	$189.60
Purchase #2	$101.61	3.613%	$105.2812	$105.28	$105.30	$105.30
Purchase #3	$23.50	3.775%	$24.3871	$24.39	$24.40	$24.40
Purchase #4	$106.42	4.629%	$111.3462	$111.35	$111.35	$111.30
Purchase #5	$234.91	12.806%	$264.9926	$264.99	$265.00	$265.00
Purchase #6	$221.92	6.436%	$236.2028	$236.20	$236.20	$236.20
Purchase #7	$155.68	8.177%	$168.41	$168.41	$168.40	$168.40
7 purchase totals =	$1,024.35		$1,100.2591	$1,100.26	$1,100.30	$1,100.20