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	$137.97	10.839%	$152.9246	$152.92	$152.90	$152.90
Purchase #2	$56.48	8.523%	$61.2938	$61.29	$61.30	$61.30
Purchase #3	$201.27	5.245%	$211.8266	$211.83	$211.85	$211.80
Purchase #4	$245.44	13.515%	$278.6112	$278.61	$278.60	$278.60
Purchase #5	$57.93	12.860%	$65.3798	$65.38	$65.40	$65.40
Purchase #6	$143.49	4.473%	$149.9083	$149.91	$149.90	$149.90
Purchase #7	$128.39	4.492%	$134.1573	$134.16	$134.15	$134.20
7 purchase totals =	$970.97		$1,054.1016	$1,054.10	$1,054.10	$1,054.10