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	$168.89	13.754%	$192.1191	$192.12	$192.10	$192.10
Purchase #2	$173.84	8.815%	$189.164	$189.16	$189.15	$189.20
Purchase #3	$82.96	3.160%	$85.5815	$85.58	$85.60	$85.60
Purchase #4	$62.38	5.314%	$65.6949	$65.69	$65.70	$65.70
Purchase #5	$73.58	13.217%	$83.3051	$83.31	$83.30	$83.30
Purchase #6	$187.59	9.143%	$204.7414	$204.74	$204.75	$204.70
Purchase #7	$174.68	8.492%	$189.5138	$189.51	$189.50	$189.50
7 purchase totals =	$923.92		$1,010.1198	$1,010.11	$1,010.10	$1,010.10