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	$171.85	7.553%	$184.8298	$184.83	$184.85	$184.80
Purchase #2	$77.91	10.770%	$86.3009	$86.30	$86.30	$86.30
Purchase #3	$61.47	9.675%	$67.4172	$67.42	$67.40	$67.40
Purchase #4	$37.38	12.674%	$42.1175	$42.12	$42.10	$42.10
Purchase #5	$83.28	6.751%	$88.9022	$88.90	$88.90	$88.90
Purchase #6	$50.93	4.309%	$53.1246	$53.12	$53.10	$53.10
Purchase #7	$131.55	3.526%	$136.1885	$136.19	$136.20	$136.20
7 purchase totals =	$614.37		$658.8807	$658.88	$658.85	$658.80