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	$20.86	5.305%	$21.9666	$21.97	$21.95	$22.00
Purchase #2	$237.89	11.735%	$265.8064	$265.81	$265.80	$265.80
Purchase #3	$238.33	10.267%	$262.7993	$262.80	$262.80	$262.80
Purchase #4	$154.91	3.206%	$159.8764	$159.88	$159.90	$159.90
Purchase #5	$171.56	4.508%	$179.2939	$179.29	$179.30	$179.30
Purchase #6	$83.75	5.284%	$88.1754	$88.18	$88.20	$88.20
Purchase #7	$31.34	3.412%	$32.4093	$32.41	$32.40	$32.40
7 purchase totals =	$938.64		$1,010.3273	$1,010.34	$1,010.35	$1,010.40