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	$106.99	11.649%	$119.4533	$119.45	$119.45	$119.50
Purchase #2	$156.59	10.327%	$172.761	$172.76	$172.75	$172.80
Purchase #3	$106.33	3.349%	$109.891	$109.89	$109.90	$109.90
Purchase #4	$20.72	10.619%	$22.9203	$22.92	$22.90	$22.90
Purchase #5	$190.71	10.673%	$211.0645	$211.06	$211.05	$211.10
Purchase #6	$184.37	7.673%	$198.5167	$198.52	$198.50	$198.50
Purchase #7	$179.28	6.790%	$191.4531	$191.45	$191.45	$191.50
7 purchase totals =	$944.99		$1,026.0599	$1,026.05	$1,026.00	$1,026.20