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	$176.67	7.506%	$189.9309	$189.93	$189.95	$189.90
Purchase #2	$180.46	6.793%	$192.7186	$192.72	$192.70	$192.70
Purchase #3	$62.55	4.431%	$65.3216	$65.32	$65.30	$65.30
Purchase #4	$40.98	10.767%	$45.3923	$45.39	$45.40	$45.40
Purchase #5	$183.30	3.261%	$189.2774	$189.28	$189.30	$189.30
Purchase #6	$141.86	3.708%	$147.1202	$147.12	$147.10	$147.10
Purchase #7	$59.86	10.105%	$65.9089	$65.91	$65.90	$65.90
7 purchase totals =	$845.68		$895.6699	$895.67	$895.65	$895.60