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	$98.56	10.601%	$109.0083	$109.01	$109.00	$109.00
Purchase #2	$110.32	3.424%	$114.0974	$114.10	$114.10	$114.10
Purchase #3	$207.66	10.272%	$228.9908	$228.99	$229.00	$229.00
Purchase #4	$54.36	9.119%	$59.3171	$59.32	$59.30	$59.30
Purchase #5	$81.66	9.491%	$89.4104	$89.41	$89.40	$89.40
Purchase #6	$30.85	13.394%	$34.982	$34.98	$35.00	$35.00
Purchase #7	$92.55	8.689%	$100.5917	$100.59	$100.60	$100.60
7 purchase totals =	$675.96		$736.3977	$736.40	$736.40	$736.40