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	$75.66	12.474%	$85.0978	$85.10	$85.10	$85.10
Purchase #2	$98.77	9.295%	$107.9507	$107.95	$107.95	$108.00
Purchase #3	$197.52	6.225%	$209.8156	$209.82	$209.80	$209.80
Purchase #4	$136.33	11.257%	$151.6767	$151.68	$151.70	$151.70
Purchase #5	$184.49	6.416%	$196.3269	$196.33	$196.35	$196.30
Purchase #6	$79.88	3.360%	$82.564	$82.56	$82.55	$82.60
Purchase #7	$237.28	13.137%	$268.4515	$268.45	$268.45	$268.50
7 purchase totals =	$1,009.93		$1,101.8832	$1,101.89	$1,101.90	$1,102.00