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	$89.71	11.198%	$99.7557	$99.76	$99.75	$99.80
Purchase #2	$240.74	5.174%	$253.1959	$253.20	$253.20	$253.20
Purchase #3	$227.31	9.488%	$248.8772	$248.88	$248.90	$248.90
Purchase #4	$153.83	7.297%	$165.055	$165.06	$165.05	$165.10
Purchase #5	$218.55	7.528%	$235.0024	$235.00	$235.00	$235.00
Purchase #6	$82.41	11.473%	$91.8649	$91.86	$91.85	$91.90
Purchase #7	$85.84	5.123%	$90.2376	$90.24	$90.25	$90.20
7 purchase totals =	$1,098.39		$1,183.9887	$1,184.00	$1,184.00	$1,184.10