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	$32.69	13.851%	$37.2179	$37.22	$37.20	$37.20
Purchase #2	$79.87	3.544%	$82.7006	$82.70	$82.70	$82.70
Purchase #3	$228.48	4.278%	$238.2544	$238.25	$238.25	$238.30
Purchase #4	$197.53	5.180%	$207.7621	$207.76	$207.75	$207.80
Purchase #5	$94.97	6.250%	$100.9056	$100.91	$100.90	$100.90
Purchase #6	$189.54	4.580%	$198.2209	$198.22	$198.20	$198.20
Purchase #7	$131.26	4.585%	$137.2783	$137.28	$137.30	$137.30
7 purchase totals =	$954.34		$1,002.3398	$1,002.34	$1,002.30	$1,002.40