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	$187.36	11.241%	$208.4211	$208.42	$208.40	$208.40
Purchase #2	$50.72	8.481%	$55.0216	$55.02	$55.00	$55.00
Purchase #3	$96.55	8.851%	$105.0956	$105.10	$105.10	$105.10
Purchase #4	$39.88	8.600%	$43.3097	$43.31	$43.30	$43.30
Purchase #5	$231.59	7.789%	$249.6285	$249.63	$249.65	$249.60
Purchase #6	$134.96	4.682%	$141.2788	$141.28	$141.30	$141.30
Purchase #7	$89.41	13.616%	$101.5841	$101.58	$101.60	$101.60
7 purchase totals =	$830.47		$904.3394	$904.34	$904.35	$904.30