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	$93.31	9.279%	$101.9682	$101.97	$101.95	$102.00
Purchase #2	$188.42	3.134%	$194.3251	$194.33	$194.35	$194.30
Purchase #3	$147.70	4.718%	$154.6685	$154.67	$154.65	$154.70
Purchase #4	$88.26	13.659%	$100.3154	$100.32	$100.30	$100.30
Purchase #5	$220.46	3.547%	$228.2797	$228.28	$228.30	$228.30
Purchase #6	$72.86	7.514%	$78.3347	$78.33	$78.35	$78.30
Purchase #7	$193.72	11.233%	$215.4806	$215.48	$215.50	$215.50
7 purchase totals =	$1,004.73		$1,073.3722	$1,073.38	$1,073.40	$1,073.40