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	$81.81	13.567%	$92.9092	$92.91	$92.90	$92.90
Purchase #2	$190.69	9.140%	$208.1191	$208.12	$208.10	$208.10
Purchase #3	$59.82	13.545%	$67.9226	$67.92	$67.90	$67.90
Purchase #4	$169.42	7.424%	$181.9977	$182.00	$182.00	$182.00
Purchase #5	$183.76	11.471%	$204.8391	$204.84	$204.85	$204.80
Purchase #6	$197.49	9.309%	$215.8743	$215.87	$215.85	$215.90
Purchase #7	$98.33	6.338%	$104.5622	$104.56	$104.55	$104.60
7 purchase totals =	$981.32		$1,076.2242	$1,076.22	$1,076.15	$1,076.20