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	$114.65	9.738%	$125.8146	$125.81	$125.80	$125.80
Purchase #2	$39.97	5.481%	$42.1608	$42.16	$42.15	$42.20
Purchase #3	$59.30	8.556%	$64.3737	$64.37	$64.35	$64.40
Purchase #4	$56.77	4.708%	$59.4427	$59.44	$59.45	$59.40
Purchase #5	$101.63	4.427%	$106.1292	$106.13	$106.15	$106.10
Purchase #6	$183.63	6.660%	$195.8598	$195.86	$195.85	$195.90
Purchase #7	$32.38	4.692%	$33.8993	$33.90	$33.90	$33.90
7 purchase totals =	$588.33		$627.6801	$627.67	$627.65	$627.70