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	$82.59	9.279%	$90.2535	$90.25	$90.25	$90.30
Purchase #2	$167.43	8.332%	$181.3803	$181.38	$181.40	$181.40
Purchase #3	$162.84	8.498%	$176.6781	$176.68	$176.70	$176.70
Purchase #4	$151.79	4.502%	$158.6236	$158.62	$158.60	$158.60
Purchase #5	$191.47	9.339%	$209.3514	$209.35	$209.35	$209.40
Purchase #6	$119.42	8.357%	$129.3999	$129.40	$129.40	$129.40
Purchase #7	$198.33	12.348%	$222.8198	$222.82	$222.80	$222.80
7 purchase totals =	$1,073.87		$1,168.5066	$1,168.50	$1,168.50	$1,168.60