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	$140.29	6.296%	$149.1227	$149.12	$149.10	$149.10
Purchase #2	$17.93	5.529%	$18.9213	$18.92	$18.90	$18.90
Purchase #3	$90.49	12.289%	$101.6103	$101.61	$101.60	$101.60
Purchase #4	$46.76	13.546%	$53.0941	$53.09	$53.10	$53.10
Purchase #5	$184.82	7.373%	$198.4468	$198.45	$198.45	$198.40
Purchase #6	$238.38	12.806%	$268.9069	$268.91	$268.90	$268.90
Purchase #7	$147.64	3.538%	$152.8635	$152.86	$152.85	$152.90
7 purchase totals =	$866.31		$942.9656	$942.96	$942.90	$942.90