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	$218.46	6.818%	$233.3546	$233.35	$233.35	$233.40
Purchase #2	$99.77	12.797%	$112.5376	$112.54	$112.55	$112.50
Purchase #3	$147.31	10.107%	$162.1986	$162.20	$162.20	$162.20
Purchase #4	$69.55	12.170%	$78.0142	$78.01	$78.00	$78.00
Purchase #5	$179.27	5.160%	$188.5203	$188.52	$188.50	$188.50
Purchase #6	$211.90	7.267%	$227.2988	$227.30	$227.30	$227.30
Purchase #7	$149.72	6.102%	$158.8559	$158.86	$158.85	$158.90
7 purchase totals =	$1,075.98		$1,160.7800	$1,160.78	$1,160.75	$1,160.80