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	$13.76	7.768%	$14.8289	$14.83	$14.85	$14.80
Purchase #2	$121.74	4.474%	$127.1866	$127.19	$127.20	$127.20
Purchase #3	$64.82	7.599%	$69.7457	$69.75	$69.75	$69.70
Purchase #4	$247.39	12.497%	$278.3063	$278.31	$278.30	$278.30
Purchase #5	$185.79	5.506%	$196.0196	$196.02	$196.00	$196.00
Purchase #6	$123.77	10.150%	$136.3327	$136.33	$136.35	$136.30
Purchase #7	$222.71	9.690%	$244.2906	$244.29	$244.30	$244.30
7 purchase totals =	$979.98		$1,066.7104	$1,066.72	$1,066.75	$1,066.60