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	$215.56	8.284%	$233.417	$233.42	$233.40	$233.40
Purchase #2	$19.57	6.753%	$20.8916	$20.89	$20.90	$20.90
Purchase #3	$90.77	6.221%	$96.4168	$96.42	$96.40	$96.40
Purchase #4	$185.26	6.681%	$197.6372	$197.64	$197.65	$197.60
Purchase #5	$167.55	3.595%	$173.5734	$173.57	$173.55	$173.60
Purchase #6	$185.36	6.241%	$196.9283	$196.93	$196.95	$196.90
Purchase #7	$89.69	12.136%	$100.5748	$100.57	$100.55	$100.60
7 purchase totals =	$953.76		$1,019.4391	$1,019.44	$1,019.40	$1,019.40