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	$67.86	8.872%	$73.8805	$73.88	$73.90	$73.90
Purchase #2	$17.33	13.347%	$19.643	$19.64	$19.65	$19.60
Purchase #3	$226.34	13.227%	$256.278	$256.28	$256.30	$256.30
Purchase #4	$174.72	8.224%	$189.089	$189.09	$189.10	$189.10
Purchase #5	$104.31	4.603%	$109.1114	$109.11	$109.10	$109.10
Purchase #6	$235.41	4.321%	$245.5821	$245.58	$245.60	$245.60
Purchase #7	$190.59	4.102%	$198.408	$198.41	$198.40	$198.40
7 purchase totals =	$1,016.56		$1,091.9920	$1,091.99	$1,092.05	$1,092.00