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	$88.51	9.172%	$96.6281	$96.63	$96.65	$96.60
Purchase #2	$54.82	11.649%	$61.206	$61.21	$61.20	$61.20
Purchase #3	$85.81	5.644%	$90.6531	$90.65	$90.65	$90.70
Purchase #4	$178.47	7.159%	$191.2467	$191.25	$191.25	$191.20
Purchase #5	$162.74	12.729%	$183.4552	$183.46	$183.45	$183.50
Purchase #6	$135.91	13.498%	$154.2551	$154.26	$154.25	$154.30
Purchase #7	$229.96	4.102%	$239.393	$239.39	$239.40	$239.40
7 purchase totals =	$936.22		$1,016.8372	$1,016.85	$1,016.85	$1,016.90