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	$176.30	3.748%	$182.9077	$182.91	$182.90	$182.90
Purchase #2	$24.92	11.142%	$27.6966	$27.70	$27.70	$27.70
Purchase #3	$12.72	12.247%	$14.2778	$14.28	$14.30	$14.30
Purchase #4	$195.38	8.586%	$212.1553	$212.16	$212.15	$212.20
Purchase #5	$145.82	7.544%	$156.8207	$156.82	$156.80	$156.80
Purchase #6	$220.37	11.471%	$245.6486	$245.65	$245.65	$245.60
Purchase #7	$85.59	4.359%	$89.3209	$89.32	$89.30	$89.30
7 purchase totals =	$861.10		$928.8276	$928.84	$928.80	$928.80