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	$154.92	10.450%	$171.1091	$171.11	$171.10	$171.10
Purchase #2	$150.37	9.773%	$165.0657	$165.07	$165.05	$165.10
Purchase #3	$110.33	9.312%	$120.6039	$120.60	$120.60	$120.60
Purchase #4	$50.87	9.332%	$55.6172	$55.62	$55.60	$55.60
Purchase #5	$176.41	5.333%	$185.8179	$185.82	$185.80	$185.80
Purchase #6	$145.80	12.828%	$164.5032	$164.50	$164.50	$164.50
Purchase #7	$99.64	13.430%	$113.0217	$113.02	$113.00	$113.00
7 purchase totals =	$888.34		$975.7387	$975.74	$975.65	$975.70