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	$228.54	9.288%	$249.7668	$249.77	$249.75	$249.80
Purchase #2	$246.27	6.336%	$261.8737	$261.87	$261.85	$261.90
Purchase #3	$54.56	5.465%	$57.5417	$57.54	$57.55	$57.50
Purchase #4	$90.84	11.326%	$101.1285	$101.13	$101.15	$101.10
Purchase #5	$240.63	4.279%	$250.9266	$250.93	$250.95	$250.90
Purchase #6	$10.96	7.723%	$11.8064	$11.81	$11.80	$11.80
Purchase #7	$77.40	11.264%	$86.1183	$86.12	$86.10	$86.10
7 purchase totals =	$949.20		$1,019.1620	$1,019.17	$1,019.15	$1,019.10