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	$64.55	10.554%	$71.3626	$71.36	$71.35	$71.40
Purchase #2	$91.84	10.241%	$101.2453	$101.25	$101.25	$101.20
Purchase #3	$175.63	11.818%	$196.386	$196.39	$196.40	$196.40
Purchase #4	$233.62	12.152%	$262.0095	$262.01	$262.00	$262.00
Purchase #5	$79.66	7.220%	$85.4115	$85.41	$85.40	$85.40
Purchase #6	$31.61	4.744%	$33.1096	$33.11	$33.10	$33.10
Purchase #7	$168.28	10.695%	$186.2775	$186.28	$186.30	$186.30
7 purchase totals =	$845.19		$935.8020	$935.81	$935.80	$935.80