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	$110.76	12.698%	$124.8243	$124.82	$124.80	$124.80
Purchase #2	$163.72	8.836%	$178.1863	$178.19	$178.20	$178.20
Purchase #3	$228.41	7.532%	$245.6138	$245.61	$245.60	$245.60
Purchase #4	$99.53	10.663%	$110.1429	$110.14	$110.15	$110.10
Purchase #5	$162.84	3.624%	$168.7413	$168.74	$168.75	$168.70
Purchase #6	$85.97	11.396%	$95.7671	$95.77	$95.75	$95.80
Purchase #7	$165.83	13.567%	$188.3282	$188.33	$188.35	$188.30
7 purchase totals =	$1,017.06		$1,111.6039	$1,111.60	$1,111.60	$1,111.50