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	$151.86	4.463%	$158.6375	$158.64	$158.65	$158.60
Purchase #2	$233.84	3.726%	$242.5529	$242.55	$242.55	$242.60
Purchase #3	$38.75	10.745%	$42.9137	$42.91	$42.90	$42.90
Purchase #4	$94.52	3.134%	$97.4823	$97.48	$97.50	$97.50
Purchase #5	$148.62	11.524%	$165.747	$165.75	$165.75	$165.70
Purchase #6	$250.35	9.260%	$273.5324	$273.53	$273.55	$273.50
Purchase #7	$19.86	4.436%	$20.741	$20.74	$20.75	$20.70
7 purchase totals =	$937.80		$1,001.6068	$1,001.60	$1,001.65	$1,001.50