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	$130.50	7.303%	$140.0304	$140.03	$140.05	$140.00
Purchase #2	$131.75	7.435%	$141.5456	$141.55	$141.55	$141.50
Purchase #3	$90.80	8.106%	$98.1602	$98.16	$98.15	$98.20
Purchase #4	$242.68	13.444%	$275.3059	$275.31	$275.30	$275.30
Purchase #5	$221.90	4.471%	$231.8211	$231.82	$231.80	$231.80
Purchase #6	$177.43	3.174%	$183.0616	$183.06	$183.05	$183.10
Purchase #7	$100.89	4.617%	$105.5481	$105.55	$105.55	$105.50
7 purchase totals =	$1,095.95		$1,175.4729	$1,175.48	$1,175.45	$1,175.40