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	$159.62	7.489%	$171.5739	$171.57	$171.55	$171.60
Purchase #2	$176.36	6.736%	$188.2396	$188.24	$188.25	$188.20
Purchase #3	$136.74	7.791%	$147.3934	$147.39	$147.40	$147.40
Purchase #4	$123.55	3.180%	$127.4789	$127.48	$127.50	$127.50
Purchase #5	$31.77	4.113%	$33.0767	$33.08	$33.10	$33.10
Purchase #6	$46.90	6.278%	$49.8444	$49.84	$49.85	$49.80
Purchase #7	$43.54	6.772%	$46.4885	$46.49	$46.50	$46.50
7 purchase totals =	$718.48		$764.0954	$764.09	$764.15	$764.10