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	$89.57	11.440%	$99.8168	$99.82	$99.80	$99.80
Purchase #2	$70.27	12.375%	$78.9659	$78.97	$78.95	$79.00
Purchase #3	$238.50	3.118%	$245.9364	$245.94	$245.95	$245.90
Purchase #4	$249.57	11.422%	$278.0759	$278.08	$278.10	$278.10
Purchase #5	$154.73	9.245%	$169.0348	$169.03	$169.05	$169.00
Purchase #6	$61.46	4.792%	$64.4052	$64.41	$64.40	$64.40
Purchase #7	$86.66	11.269%	$96.4257	$96.43	$96.45	$96.40
7 purchase totals =	$950.76		$1,032.6607	$1,032.68	$1,032.70	$1,032.60