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	$249.41	7.647%	$268.4824	$268.48	$268.50	$268.50
Purchase #2	$115.81	6.624%	$123.4813	$123.48	$123.50	$123.50
Purchase #3	$129.28	4.854%	$135.5553	$135.56	$135.55	$135.60
Purchase #4	$181.91	7.814%	$196.1244	$196.12	$196.10	$196.10
Purchase #5	$83.33	9.818%	$91.5113	$91.51	$91.50	$91.50
Purchase #6	$182.41	13.420%	$206.8894	$206.89	$206.90	$206.90
Purchase #7	$25.85	7.501%	$27.789	$27.79	$27.80	$27.80
7 purchase totals =	$968.00		$1,049.8331	$1,049.83	$1,049.85	$1,049.90