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	$212.60	7.820%	$229.2253	$229.23	$229.25	$229.20
Purchase #2	$144.66	4.301%	$150.8818	$150.88	$150.90	$150.90
Purchase #3	$198.50	10.194%	$218.7351	$218.74	$218.75	$218.70
Purchase #4	$76.58	3.736%	$79.441	$79.44	$79.45	$79.40
Purchase #5	$105.74	5.242%	$111.2829	$111.28	$111.30	$111.30
Purchase #6	$148.72	12.533%	$167.3591	$167.36	$167.35	$167.40
Purchase #7	$247.63	9.275%	$270.5977	$270.60	$270.60	$270.60
7 purchase totals =	$1,134.43		$1,227.5229	$1,227.53	$1,227.60	$1,227.50