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	$32.80	5.367%	$34.5604	$34.56	$34.55	$34.60
Purchase #2	$215.56	12.718%	$242.9749	$242.97	$242.95	$243.00
Purchase #3	$119.33	6.631%	$127.2428	$127.24	$127.25	$127.20
Purchase #4	$49.98	9.562%	$54.7591	$54.76	$54.75	$54.80
Purchase #5	$160.72	13.261%	$182.0331	$182.03	$182.05	$182.00
Purchase #6	$56.93	4.589%	$59.5425	$59.54	$59.55	$59.50
Purchase #7	$53.86	10.809%	$59.6817	$59.68	$59.70	$59.70
7 purchase totals =	$689.18		$760.7945	$760.78	$760.80	$760.80