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	$141.47	5.526%	$149.2876	$149.29	$149.30	$149.30
Purchase #2	$8.87	7.382%	$9.5248	$9.52	$9.50	$9.50
Purchase #3	$203.89	8.156%	$220.5193	$220.52	$220.50	$220.50
Purchase #4	$160.79	6.683%	$171.5356	$171.54	$171.55	$171.50
Purchase #5	$72.50	10.312%	$79.9762	$79.98	$80.00	$80.00
Purchase #6	$101.56	3.675%	$105.2923	$105.29	$105.30	$105.30
Purchase #7	$53.93	9.642%	$59.1299	$59.13	$59.15	$59.10
7 purchase totals =	$743.01		$795.2657	$795.27	$795.30	$795.20