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	$164.43	9.541%	$180.1183	$180.12	$180.10	$180.10
Purchase #2	$33.40	9.570%	$36.5964	$36.60	$36.60	$36.60
Purchase #3	$214.63	6.644%	$228.89	$228.89	$228.90	$228.90
Purchase #4	$122.88	3.739%	$127.4745	$127.47	$127.45	$127.50
Purchase #5	$175.56	6.600%	$187.147	$187.15	$187.15	$187.10
Purchase #6	$120.73	11.746%	$134.9109	$134.91	$134.90	$134.90
Purchase #7	$156.25	9.614%	$171.2719	$171.27	$171.25	$171.30
7 purchase totals =	$987.88		$1,066.4090	$1,066.41	$1,066.35	$1,066.40