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	$64.53	11.370%	$71.8671	$71.87	$71.85	$71.90
Purchase #2	$131.62	13.742%	$149.7072	$149.71	$149.70	$149.70
Purchase #3	$140.73	8.245%	$152.3332	$152.33	$152.35	$152.30
Purchase #4	$234.59	9.662%	$257.2561	$257.26	$257.25	$257.30
Purchase #5	$215.66	6.543%	$229.7706	$229.77	$229.75	$229.80
Purchase #6	$100.66	8.773%	$109.4909	$109.49	$109.50	$109.50
Purchase #7	$74.98	4.584%	$78.4171	$78.42	$78.40	$78.40
7 purchase totals =	$962.77		$1,048.8422	$1,048.85	$1,048.80	$1,048.90