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	$141.79	10.618%	$156.8453	$156.85	$156.85	$156.80
Purchase #2	$25.81	10.864%	$28.614	$28.61	$28.60	$28.60
Purchase #3	$61.74	6.153%	$65.5389	$65.54	$65.55	$65.50
Purchase #4	$156.94	5.283%	$165.2311	$165.23	$165.25	$165.20
Purchase #5	$198.62	12.436%	$223.3204	$223.32	$223.30	$223.30
Purchase #6	$73.86	9.631%	$80.9735	$80.97	$80.95	$81.00
Purchase #7	$14.31	11.109%	$15.8997	$15.90	$15.90	$15.90
7 purchase totals =	$673.07		$736.4229	$736.42	$736.40	$736.30