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	$167.82	6.265%	$178.3339	$178.33	$178.35	$178.30
Purchase #2	$49.92	8.421%	$54.1238	$54.12	$54.10	$54.10
Purchase #3	$126.50	13.287%	$143.3081	$143.31	$143.30	$143.30
Purchase #4	$122.63	11.502%	$136.7349	$136.73	$136.75	$136.70
Purchase #5	$188.80	4.317%	$196.9505	$196.95	$196.95	$197.00
Purchase #6	$187.40	4.600%	$196.0204	$196.02	$196.00	$196.00
Purchase #7	$81.32	11.813%	$90.9263	$90.93	$90.95	$90.90
7 purchase totals =	$924.39		$996.3979	$996.39	$996.40	$996.30