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	$83.92	7.533%	$90.2417	$90.24	$90.25	$90.20
Purchase #2	$139.52	8.275%	$151.0653	$151.07	$151.05	$151.10
Purchase #3	$182.90	6.565%	$194.9074	$194.91	$194.90	$194.90
Purchase #4	$119.27	9.744%	$130.8917	$130.89	$130.90	$130.90
Purchase #5	$95.87	3.160%	$98.8995	$98.90	$98.90	$98.90
Purchase #6	$79.64	7.465%	$85.5851	$85.59	$85.60	$85.60
Purchase #7	$231.59	9.424%	$253.415	$253.42	$253.40	$253.40
7 purchase totals =	$932.71		$1,005.0057	$1,005.02	$1,005.00	$1,005.00