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	$168.90	4.869%	$177.1237	$177.12	$177.10	$177.10
Purchase #2	$109.76	12.223%	$123.176	$123.18	$123.20	$123.20
Purchase #3	$52.32	7.560%	$56.2754	$56.28	$56.30	$56.30
Purchase #4	$226.27	8.112%	$244.625	$244.63	$244.65	$244.60
Purchase #5	$217.51	6.210%	$231.0174	$231.02	$231.00	$231.00
Purchase #6	$36.27	11.173%	$40.3224	$40.32	$40.30	$40.30
Purchase #7	$143.79	4.722%	$150.5798	$150.58	$150.60	$150.60
7 purchase totals =	$954.82		$1,023.1197	$1,023.13	$1,023.15	$1,023.10