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	$93.34	11.131%	$103.7297	$103.73	$103.75	$103.70
Purchase #2	$145.50	9.743%	$159.6761	$159.68	$159.70	$159.70
Purchase #3	$104.78	10.284%	$115.5556	$115.56	$115.55	$115.60
Purchase #4	$201.91	13.797%	$229.7675	$229.77	$229.75	$229.80
Purchase #5	$171.80	11.462%	$191.4917	$191.49	$191.50	$191.50
Purchase #6	$154.59	11.135%	$171.8036	$171.80	$171.80	$171.80
Purchase #7	$92.96	13.551%	$105.557	$105.56	$105.55	$105.60
7 purchase totals =	$964.88		$1,077.5812	$1,077.59	$1,077.60	$1,077.70