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	$174.32	5.331%	$183.613	$183.61	$183.60	$183.60
Purchase #2	$72.91	6.839%	$77.8963	$77.90	$77.90	$77.90
Purchase #3	$245.73	11.512%	$274.0184	$274.02	$274.00	$274.00
Purchase #4	$53.72	11.436%	$59.8634	$59.86	$59.85	$59.90
Purchase #5	$90.29	9.117%	$98.5217	$98.52	$98.50	$98.50
Purchase #6	$76.40	13.399%	$86.6368	$86.64	$86.65	$86.60
Purchase #7	$8.73	6.125%	$9.2647	$9.26	$9.25	$9.30
7 purchase totals =	$722.10		$789.8143	$789.81	$789.75	$789.80