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	$169.52	9.661%	$185.8973	$185.90	$185.90	$185.90
Purchase #2	$80.60	13.171%	$91.2158	$91.22	$91.20	$91.20
Purchase #3	$67.46	6.312%	$71.7181	$71.72	$71.70	$71.70
Purchase #4	$104.91	10.867%	$116.3106	$116.31	$116.30	$116.30
Purchase #5	$25.83	10.465%	$28.5331	$28.53	$28.55	$28.50
Purchase #6	$139.84	7.451%	$150.2595	$150.26	$150.25	$150.30
Purchase #7	$89.72	3.434%	$92.801	$92.80	$92.80	$92.80
7 purchase totals =	$677.88		$736.7354	$736.74	$736.70	$736.70