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	$98.55	11.251%	$109.6379	$109.64	$109.65	$109.60
Purchase #2	$225.75	7.471%	$242.6158	$242.62	$242.60	$242.60
Purchase #3	$38.73	9.678%	$42.4783	$42.48	$42.50	$42.50
Purchase #4	$81.36	5.781%	$86.0634	$86.06	$86.05	$86.10
Purchase #5	$53.30	13.423%	$60.4545	$60.45	$60.45	$60.50
Purchase #6	$25.50	6.483%	$27.1532	$27.15	$27.15	$27.20
Purchase #7	$169.90	4.863%	$178.1622	$178.16	$178.15	$178.20
7 purchase totals =	$693.09		$746.5653	$746.56	$746.55	$746.70