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	$238.54	12.594%	$268.5817	$268.58	$268.60	$268.60
Purchase #2	$149.85	9.448%	$164.0078	$164.01	$164.00	$164.00
Purchase #3	$187.69	7.666%	$202.0783	$202.08	$202.10	$202.10
Purchase #4	$11.89	3.494%	$12.3054	$12.31	$12.30	$12.30
Purchase #5	$85.39	13.168%	$96.6342	$96.63	$96.65	$96.60
Purchase #6	$155.76	8.183%	$168.5058	$168.51	$168.50	$168.50
Purchase #7	$142.51	13.780%	$162.1479	$162.15	$162.15	$162.10
7 purchase totals =	$971.63		$1,074.2611	$1,074.27	$1,074.30	$1,074.20