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	$184.99	6.447%	$196.9163	$196.92	$196.90	$196.90
Purchase #2	$59.80	9.335%	$65.3823	$65.38	$65.40	$65.40
Purchase #3	$221.98	9.143%	$242.2756	$242.28	$242.30	$242.30
Purchase #4	$92.58	10.227%	$102.0482	$102.05	$102.05	$102.00
Purchase #5	$54.33	8.821%	$59.1224	$59.12	$59.10	$59.10
Purchase #6	$165.90	10.257%	$182.9164	$182.92	$182.90	$182.90
Purchase #7	$164.82	3.801%	$171.0848	$171.08	$171.10	$171.10
7 purchase totals =	$944.40		$1,019.7460	$1,019.75	$1,019.75	$1,019.70