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	$104.53	9.153%	$114.0976	$114.10	$114.10	$114.10
Purchase #2	$67.49	5.400%	$71.1345	$71.13	$71.15	$71.10
Purchase #3	$95.77	4.760%	$100.3287	$100.33	$100.35	$100.30
Purchase #4	$201.86	4.485%	$210.9134	$210.91	$210.90	$210.90
Purchase #5	$194.77	7.149%	$208.6941	$208.69	$208.70	$208.70
Purchase #6	$77.98	4.366%	$81.3846	$81.38	$81.40	$81.40
Purchase #7	$199.88	11.681%	$223.228	$223.23	$223.25	$223.20
7 purchase totals =	$942.28		$1,009.7809	$1,009.77	$1,009.85	$1,009.70