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	$82.38	10.636%	$91.1419	$91.14	$91.15	$91.10
Purchase #2	$206.25	4.130%	$214.7681	$214.77	$214.75	$214.80
Purchase #3	$154.89	13.199%	$175.3339	$175.33	$175.35	$175.30
Purchase #4	$75.31	4.728%	$78.8707	$78.87	$78.85	$78.90
Purchase #5	$28.94	13.277%	$32.7824	$32.78	$32.80	$32.80
Purchase #6	$198.62	3.113%	$204.803	$204.80	$204.80	$204.80
Purchase #7	$214.40	4.557%	$224.1702	$224.17	$224.15	$224.20
7 purchase totals =	$960.79		$1,021.8702	$1,021.86	$1,021.85	$1,021.90