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	$141.38	10.573%	$156.3281	$156.33	$156.35	$156.30
Purchase #2	$83.41	6.264%	$88.6348	$88.63	$88.65	$88.60
Purchase #3	$212.38	13.597%	$241.2573	$241.26	$241.25	$241.30
Purchase #4	$151.26	13.556%	$171.7648	$171.76	$171.75	$171.80
Purchase #5	$101.87	9.132%	$111.1728	$111.17	$111.15	$111.20
Purchase #6	$86.49	11.539%	$96.4701	$96.47	$96.45	$96.50
Purchase #7	$78.99	7.452%	$84.8763	$84.88	$84.90	$84.90
7 purchase totals =	$855.78		$950.5042	$950.50	$950.50	$950.60