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	$50.38	6.233%	$53.5202	$53.52	$53.50	$53.50
Purchase #2	$76.59	11.407%	$85.3266	$85.33	$85.35	$85.30
Purchase #3	$219.58	4.649%	$229.7883	$229.79	$229.80	$229.80
Purchase #4	$138.45	8.773%	$150.5962	$150.60	$150.60	$150.60
Purchase #5	$103.62	9.279%	$113.2349	$113.23	$113.25	$113.20
Purchase #6	$223.63	10.556%	$247.2364	$247.24	$247.25	$247.20
Purchase #7	$159.70	7.613%	$171.858	$171.86	$171.85	$171.90
7 purchase totals =	$971.95		$1,051.5606	$1,051.57	$1,051.60	$1,051.50