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	$161.94	5.845%	$171.4054	$171.41	$171.40	$171.40
Purchase #2	$22.27	11.345%	$24.7965	$24.80	$24.80	$24.80
Purchase #3	$80.85	6.742%	$86.3009	$86.30	$86.30	$86.30
Purchase #4	$86.86	5.466%	$91.6078	$91.61	$91.60	$91.60
Purchase #5	$235.82	5.556%	$248.9222	$248.92	$248.90	$248.90
Purchase #6	$90.30	12.368%	$101.4683	$101.47	$101.45	$101.50
Purchase #7	$62.49	7.393%	$67.1099	$67.11	$67.10	$67.10
7 purchase totals =	$740.53		$791.6110	$791.62	$791.55	$791.60