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	$147.63	10.246%	$162.7562	$162.76	$162.75	$162.80
Purchase #2	$241.89	7.468%	$259.9543	$259.95	$259.95	$260.00
Purchase #3	$179.41	6.399%	$190.8904	$190.89	$190.90	$190.90
Purchase #4	$32.56	13.828%	$37.0624	$37.06	$37.05	$37.10
Purchase #5	$238.45	13.841%	$271.4539	$271.45	$271.45	$271.50
Purchase #6	$77.85	10.765%	$86.2306	$86.23	$86.25	$86.20
Purchase #7	$194.77	8.173%	$210.6886	$210.69	$210.70	$210.70
7 purchase totals =	$1,112.56		$1,219.0364	$1,219.03	$1,219.05	$1,219.20