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	$65.46	3.741%	$67.9089	$67.91	$67.90	$67.90
Purchase #2	$131.72	9.820%	$144.6549	$144.65	$144.65	$144.70
Purchase #3	$31.31	12.603%	$35.256	$35.26	$35.25	$35.30
Purchase #4	$73.75	12.265%	$82.7954	$82.80	$82.80	$82.80
Purchase #5	$191.27	4.486%	$199.8504	$199.85	$199.85	$199.90
Purchase #6	$245.69	4.228%	$256.0778	$256.08	$256.10	$256.10
Purchase #7	$51.42	12.528%	$57.8619	$57.86	$57.85	$57.90
7 purchase totals =	$790.62		$844.4053	$844.41	$844.40	$844.60