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	$173.56	5.367%	$182.875	$182.88	$182.90	$182.90
Purchase #2	$84.53	13.528%	$95.9652	$95.97	$95.95	$96.00
Purchase #3	$124.27	11.873%	$139.0246	$139.02	$139.00	$139.00
Purchase #4	$57.75	13.685%	$65.6531	$65.65	$65.65	$65.70
Purchase #5	$79.71	13.782%	$90.6956	$90.70	$90.70	$90.70
Purchase #6	$98.27	13.466%	$111.503	$111.50	$111.50	$111.50
Purchase #7	$165.77	9.836%	$182.0751	$182.08	$182.10	$182.10
7 purchase totals =	$783.86		$867.7916	$867.80	$867.80	$867.90