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	$96.31	3.549%	$99.728	$99.73	$99.75	$99.70
Purchase #2	$191.85	10.558%	$212.1055	$212.11	$212.10	$212.10
Purchase #3	$57.90	3.346%	$59.8373	$59.84	$59.85	$59.80
Purchase #4	$11.90	9.288%	$13.0053	$13.01	$13.00	$13.00
Purchase #5	$39.82	3.612%	$41.2583	$41.26	$41.25	$41.30
Purchase #6	$80.84	3.613%	$83.7607	$83.76	$83.75	$83.80
Purchase #7	$86.41	10.613%	$95.5807	$95.58	$95.60	$95.60
7 purchase totals =	$565.03		$605.2758	$605.29	$605.30	$605.30