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	$54.27	13.504%	$61.5986	$61.60	$61.60	$61.60
Purchase #2	$152.45	6.430%	$162.2525	$162.25	$162.25	$162.30
Purchase #3	$76.51	8.134%	$82.7333	$82.73	$82.75	$82.70
Purchase #4	$171.39	6.364%	$182.2973	$182.30	$182.30	$182.30
Purchase #5	$100.33	9.691%	$110.053	$110.05	$110.05	$110.10
Purchase #6	$101.40	7.614%	$109.1206	$109.12	$109.10	$109.10
Purchase #7	$59.95	4.683%	$62.7575	$62.76	$62.75	$62.80
7 purchase totals =	$716.30		$770.8128	$770.81	$770.80	$770.90