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	$191.72	4.669%	$200.6714	$200.67	$200.65	$200.70
Purchase #2	$91.82	8.134%	$99.2886	$99.29	$99.30	$99.30
Purchase #3	$64.49	13.313%	$73.0756	$73.08	$73.10	$73.10
Purchase #4	$6.88	3.654%	$7.1314	$7.13	$7.15	$7.10
Purchase #5	$231.54	13.665%	$263.1799	$263.18	$263.20	$263.20
Purchase #6	$84.49	5.804%	$89.3938	$89.39	$89.40	$89.40
Purchase #7	$60.39	4.347%	$63.0152	$63.02	$63.00	$63.00
7 purchase totals =	$731.33		$795.7559	$795.76	$795.80	$795.80