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	$52.41	13.268%	$59.3638	$59.36	$59.35	$59.40
Purchase #2	$6.46	12.583%	$7.2729	$7.27	$7.25	$7.30
Purchase #3	$167.86	11.140%	$186.5596	$186.56	$186.55	$186.60
Purchase #4	$95.25	12.512%	$107.1677	$107.17	$107.15	$107.20
Purchase #5	$156.95	7.106%	$168.1029	$168.10	$168.10	$168.10
Purchase #6	$213.98	6.723%	$228.3659	$228.37	$228.35	$228.40
Purchase #7	$207.69	10.489%	$229.4746	$229.47	$229.45	$229.50
7 purchase totals =	$900.60		$986.3074	$986.30	$986.20	$986.50