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	$200.69	5.408%	$211.5433	$211.54	$211.55	$211.50
Purchase #2	$44.94	3.339%	$46.4405	$46.44	$46.45	$46.40
Purchase #3	$158.35	6.374%	$168.4432	$168.44	$168.45	$168.40
Purchase #4	$28.52	11.282%	$31.7376	$31.74	$31.75	$31.70
Purchase #5	$51.94	10.437%	$57.361	$57.36	$57.35	$57.40
Purchase #6	$64.95	12.368%	$72.983	$72.98	$73.00	$73.00
Purchase #7	$131.76	11.610%	$147.0573	$147.06	$147.05	$147.10
7 purchase totals =	$681.15		$735.5659	$735.56	$735.60	$735.50