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	$52.33	8.630%	$56.8461	$56.85	$56.85	$56.80
Purchase #2	$93.96	3.348%	$97.1058	$97.11	$97.10	$97.10
Purchase #3	$121.99	4.205%	$127.1197	$127.12	$127.10	$127.10
Purchase #4	$182.84	12.820%	$206.2801	$206.28	$206.30	$206.30
Purchase #5	$213.88	12.763%	$241.1775	$241.18	$241.20	$241.20
Purchase #6	$168.73	3.585%	$174.779	$174.78	$174.80	$174.80
Purchase #7	$91.86	8.804%	$99.9474	$99.95	$99.95	$99.90
7 purchase totals =	$925.59		$1,003.2556	$1,003.27	$1,003.30	$1,003.20