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	$85.79	5.645%	$90.6328	$90.63	$90.65	$90.60
Purchase #2	$68.31	12.368%	$76.7586	$76.76	$76.75	$76.80
Purchase #3	$217.82	12.626%	$245.322	$245.32	$245.30	$245.30
Purchase #4	$89.71	7.231%	$96.1969	$96.20	$96.20	$96.20
Purchase #5	$128.93	4.262%	$134.425	$134.43	$134.45	$134.40
Purchase #6	$166.94	11.218%	$185.6673	$185.67	$185.65	$185.70
Purchase #7	$165.73	4.317%	$172.8846	$172.88	$172.90	$172.90
7 purchase totals =	$923.23		$1,001.8872	$1,001.89	$1,001.90	$1,001.90