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	$87.59	3.593%	$90.7371	$90.74	$90.75	$90.70
Purchase #2	$158.96	6.242%	$168.8823	$168.88	$168.90	$168.90
Purchase #3	$211.89	5.124%	$222.7472	$222.75	$222.75	$222.70
Purchase #4	$156.84	8.334%	$169.911	$169.91	$169.90	$169.90
Purchase #5	$181.61	5.328%	$191.2862	$191.29	$191.30	$191.30
Purchase #6	$244.51	12.737%	$275.6532	$275.65	$275.65	$275.70
Purchase #7	$174.66	8.219%	$189.0153	$189.02	$189.00	$189.00
7 purchase totals =	$1,216.06		$1,308.2323	$1,308.24	$1,308.25	$1,308.20