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	$202.45	8.787%	$220.2393	$220.24	$220.25	$220.20
Purchase #2	$205.25	11.552%	$228.9605	$228.96	$228.95	$229.00
Purchase #3	$56.84	9.735%	$62.3734	$62.37	$62.35	$62.40
Purchase #4	$127.56	3.289%	$131.7554	$131.76	$131.75	$131.80
Purchase #5	$6.91	6.793%	$7.3794	$7.38	$7.40	$7.40
Purchase #6	$206.41	7.685%	$222.2726	$222.27	$222.25	$222.30
Purchase #7	$197.46	7.330%	$211.9338	$211.93	$211.95	$211.90
7 purchase totals =	$1,002.88		$1,084.9144	$1,084.91	$1,084.90	$1,085.00