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	$89.72	9.482%	$98.2273	$98.23	$98.25	$98.20
Purchase #2	$170.91	11.534%	$190.6228	$190.62	$190.60	$190.60
Purchase #3	$79.60	4.762%	$83.3906	$83.39	$83.40	$83.40
Purchase #4	$147.31	4.765%	$154.3293	$154.33	$154.35	$154.30
Purchase #5	$51.95	4.630%	$54.3553	$54.36	$54.35	$54.40
Purchase #6	$177.46	11.763%	$198.3346	$198.33	$198.35	$198.30
Purchase #7	$149.37	11.179%	$166.0681	$166.07	$166.05	$166.10
7 purchase totals =	$866.32		$945.3280	$945.33	$945.35	$945.30