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	$213.74	6.698%	$228.0563	$228.06	$228.05	$228.10
Purchase #2	$99.39	4.662%	$104.0236	$104.02	$104.00	$104.00
Purchase #3	$188.92	4.162%	$196.7829	$196.78	$196.80	$196.80
Purchase #4	$21.70	10.441%	$23.9657	$23.97	$23.95	$24.00
Purchase #5	$111.30	11.218%	$123.7856	$123.79	$123.80	$123.80
Purchase #6	$159.32	13.309%	$180.5239	$180.52	$180.50	$180.50
Purchase #7	$69.64	13.308%	$78.9077	$78.91	$78.90	$78.90
7 purchase totals =	$864.01		$936.0457	$936.05	$936.00	$936.10