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	$235.45	8.245%	$254.8629	$254.86	$254.85	$254.90
Purchase #2	$171.41	8.441%	$185.8787	$185.88	$185.90	$185.90
Purchase #3	$221.26	10.229%	$243.8927	$243.89	$243.90	$243.90
Purchase #4	$231.72	13.682%	$263.4239	$263.42	$263.40	$263.40
Purchase #5	$41.80	10.574%	$46.2199	$46.22	$46.20	$46.20
Purchase #6	$224.42	13.710%	$255.188	$255.19	$255.20	$255.20
Purchase #7	$109.60	8.867%	$119.3182	$119.32	$119.30	$119.30
7 purchase totals =	$1,235.66		$1,368.7843	$1,368.78	$1,368.75	$1,368.80