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	$32.64	13.419%	$37.02	$37.02	$37.00	$37.00
Purchase #2	$181.94	4.469%	$190.0709	$190.07	$190.05	$190.10
Purchase #3	$241.85	8.112%	$261.4689	$261.47	$261.45	$261.50
Purchase #4	$129.33	13.743%	$147.1038	$147.10	$147.10	$147.10
Purchase #5	$29.31	4.788%	$30.7134	$30.71	$30.70	$30.70
Purchase #6	$134.77	5.213%	$141.7956	$141.80	$141.80	$141.80
Purchase #7	$196.85	7.218%	$211.0586	$211.06	$211.05	$211.10
7 purchase totals =	$946.69		$1,019.2312	$1,019.23	$1,019.15	$1,019.30