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	$69.30	3.640%	$71.8225	$71.82	$71.80	$71.80
Purchase #2	$49.73	6.124%	$52.7755	$52.78	$52.80	$52.80
Purchase #3	$237.88	4.282%	$248.066	$248.07	$248.05	$248.10
Purchase #4	$175.28	4.171%	$182.5909	$182.59	$182.60	$182.60
Purchase #5	$32.30	3.167%	$33.3229	$33.32	$33.30	$33.30
Purchase #6	$105.47	6.400%	$112.2201	$112.22	$112.20	$112.20
Purchase #7	$154.45	5.141%	$162.3903	$162.39	$162.40	$162.40
7 purchase totals =	$824.41		$863.1882	$863.19	$863.15	$863.20