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	$90.50	6.274%	$96.178	$96.18	$96.20	$96.20
Purchase #2	$160.80	8.445%	$174.3796	$174.38	$174.40	$174.40
Purchase #3	$165.38	8.718%	$179.7978	$179.80	$179.80	$179.80
Purchase #4	$150.29	9.802%	$165.0214	$165.02	$165.00	$165.00
Purchase #5	$90.64	4.506%	$94.7242	$94.72	$94.70	$94.70
Purchase #6	$88.93	11.161%	$98.8555	$98.86	$98.85	$98.90
Purchase #7	$203.42	3.834%	$211.2191	$211.22	$211.20	$211.20
7 purchase totals =	$949.96		$1,020.1756	$1,020.18	$1,020.15	$1,020.20