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	$84.34	4.427%	$88.0737	$88.07	$88.05	$88.10
Purchase #2	$147.90	11.510%	$164.9233	$164.92	$164.90	$164.90
Purchase #3	$55.31	4.828%	$57.9804	$57.98	$58.00	$58.00
Purchase #4	$143.93	5.323%	$151.5914	$151.59	$151.60	$151.60
Purchase #5	$150.34	3.547%	$155.6726	$155.67	$155.65	$155.70
Purchase #6	$173.36	11.815%	$193.8425	$193.84	$193.85	$193.80
Purchase #7	$68.77	5.489%	$72.5448	$72.54	$72.55	$72.50
7 purchase totals =	$823.95		$884.6287	$884.61	$884.60	$884.60