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	$40.60	10.255%	$44.7635	$44.76	$44.75	$44.80
Purchase #2	$119.28	6.762%	$127.3457	$127.35	$127.35	$127.30
Purchase #3	$140.60	3.251%	$145.1709	$145.17	$145.15	$145.20
Purchase #4	$59.62	8.380%	$64.6162	$64.62	$64.60	$64.60
Purchase #5	$72.79	12.461%	$81.8604	$81.86	$81.85	$81.90
Purchase #6	$223.66	9.279%	$244.4134	$244.41	$244.40	$244.40
Purchase #7	$67.40	7.568%	$72.5008	$72.50	$72.50	$72.50
7 purchase totals =	$723.95		$780.6709	$780.67	$780.60	$780.70