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	$188.73	5.264%	$198.6647	$198.66	$198.65	$198.70
Purchase #2	$194.29	13.384%	$220.2938	$220.29	$220.30	$220.30
Purchase #3	$116.66	9.355%	$127.5735	$127.57	$127.55	$127.60
Purchase #4	$238.41	13.443%	$270.4595	$270.46	$270.45	$270.50
Purchase #5	$112.31	9.602%	$123.094	$123.09	$123.10	$123.10
Purchase #6	$26.77	12.445%	$30.1015	$30.10	$30.10	$30.10
Purchase #7	$65.69	9.534%	$71.9529	$71.95	$71.95	$72.00
7 purchase totals =	$942.86		$1,042.1399	$1,042.12	$1,042.10	$1,042.30