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	$72.76	8.206%	$78.7307	$78.73	$78.75	$78.70
Purchase #2	$65.29	10.861%	$72.3811	$72.38	$72.40	$72.40
Purchase #3	$150.26	10.591%	$166.174	$166.17	$166.15	$166.20
Purchase #4	$110.55	12.831%	$124.7347	$124.73	$124.75	$124.70
Purchase #5	$162.32	5.257%	$170.8532	$170.85	$170.85	$170.90
Purchase #6	$196.61	11.471%	$219.1631	$219.16	$219.15	$219.20
Purchase #7	$203.98	8.196%	$220.6982	$220.70	$220.70	$220.70
7 purchase totals =	$961.77		$1,052.7350	$1,052.72	$1,052.75	$1,052.80