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	$191.96	4.830%	$201.2317	$201.23	$201.25	$201.20
Purchase #2	$215.73	5.800%	$228.2423	$228.24	$228.25	$228.20
Purchase #3	$169.27	7.328%	$181.6741	$181.67	$181.65	$181.70
Purchase #4	$245.83	13.868%	$279.9217	$279.92	$279.90	$279.90
Purchase #5	$17.47	6.238%	$18.5598	$18.56	$18.55	$18.60
Purchase #6	$147.55	6.320%	$156.8752	$156.88	$156.90	$156.90
Purchase #7	$106.51	11.641%	$118.9088	$118.91	$118.90	$118.90
7 purchase totals =	$1,094.32		$1,185.4136	$1,185.41	$1,185.40	$1,185.40