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	$211.28	3.701%	$219.0995	$219.10	$219.10	$219.10
Purchase #2	$241.46	5.288%	$254.2284	$254.23	$254.25	$254.20
Purchase #3	$176.75	10.346%	$195.0366	$195.04	$195.05	$195.00
Purchase #4	$92.58	13.617%	$105.1866	$105.19	$105.20	$105.20
Purchase #5	$107.61	3.446%	$111.3182	$111.32	$111.30	$111.30
Purchase #6	$151.89	8.671%	$165.0604	$165.06	$165.05	$165.10
Purchase #7	$38.99	7.626%	$41.9634	$41.96	$41.95	$42.00
7 purchase totals =	$1,020.56		$1,091.8931	$1,091.90	$1,091.90	$1,091.90