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	$168.36	9.103%	$183.6858	$183.69	$183.70	$183.70
Purchase #2	$60.47	7.113%	$64.7712	$64.77	$64.75	$64.80
Purchase #3	$79.86	11.721%	$89.2204	$89.22	$89.20	$89.20
Purchase #4	$108.63	9.303%	$118.7358	$118.74	$118.75	$118.70
Purchase #5	$102.58	8.308%	$111.1023	$111.10	$111.10	$111.10
Purchase #6	$172.65	6.372%	$183.6513	$183.65	$183.65	$183.70
Purchase #7	$92.28	6.524%	$98.3003	$98.30	$98.30	$98.30
7 purchase totals =	$784.83		$849.4671	$849.47	$849.45	$849.50