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	$144.47	6.497%	$153.8562	$153.86	$153.85	$153.90
Purchase #2	$222.58	8.611%	$241.7464	$241.75	$241.75	$241.70
Purchase #3	$99.43	9.764%	$109.1383	$109.14	$109.15	$109.10
Purchase #4	$186.47	3.581%	$193.1475	$193.15	$193.15	$193.10
Purchase #5	$159.71	3.488%	$165.2807	$165.28	$165.30	$165.30
Purchase #6	$99.52	3.852%	$103.3535	$103.35	$103.35	$103.40
Purchase #7	$139.36	8.404%	$151.0718	$151.07	$151.05	$151.10
7 purchase totals =	$1,051.54		$1,117.5944	$1,117.60	$1,117.60	$1,117.60