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	$173.91	8.711%	$189.0593	$189.06	$189.05	$189.10
Purchase #2	$242.83	12.796%	$273.9025	$273.90	$273.90	$273.90
Purchase #3	$155.60	7.516%	$167.2949	$167.29	$167.30	$167.30
Purchase #4	$82.26	11.813%	$91.9774	$91.98	$92.00	$92.00
Purchase #5	$93.39	12.380%	$104.9517	$104.95	$104.95	$105.00
Purchase #6	$84.59	11.405%	$94.2375	$94.24	$94.25	$94.20
Purchase #7	$89.76	7.621%	$96.6006	$96.60	$96.60	$96.60
7 purchase totals =	$922.34		$1,018.0239	$1,018.02	$1,018.05	$1,018.10