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	$188.94	8.260%	$204.5464	$204.55	$204.55	$204.50
Purchase #2	$167.84	4.791%	$175.8812	$175.88	$175.90	$175.90
Purchase #3	$131.28	8.363%	$142.2589	$142.26	$142.25	$142.30
Purchase #4	$99.91	5.385%	$105.2902	$105.29	$105.30	$105.30
Purchase #5	$180.29	6.377%	$191.7871	$191.79	$191.80	$191.80
Purchase #6	$61.55	7.205%	$65.9847	$65.98	$66.00	$66.00
Purchase #7	$215.79	4.462%	$225.4185	$225.42	$225.40	$225.40
7 purchase totals =	$1,045.60		$1,111.1670	$1,111.17	$1,111.20	$1,111.20