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	$160.30	11.739%	$179.1176	$179.12	$179.10	$179.10
Purchase #2	$199.25	3.824%	$206.8693	$206.87	$206.85	$206.90
Purchase #3	$176.92	7.180%	$189.6229	$189.62	$189.60	$189.60
Purchase #4	$103.26	6.446%	$109.9161	$109.92	$109.90	$109.90
Purchase #5	$95.72	11.448%	$106.678	$106.68	$106.70	$106.70
Purchase #6	$236.39	6.111%	$250.8358	$250.84	$250.85	$250.80
Purchase #7	$20.45	7.150%	$21.9122	$21.91	$21.90	$21.90
7 purchase totals =	$992.29		$1,064.9519	$1,064.96	$1,064.90	$1,064.90