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	$48.86	10.839%	$54.1559	$54.16	$54.15	$54.20
Purchase #2	$186.50	6.676%	$198.9507	$198.95	$198.95	$199.00
Purchase #3	$226.51	12.626%	$255.1092	$255.11	$255.10	$255.10
Purchase #4	$45.84	7.485%	$49.2711	$49.27	$49.25	$49.30
Purchase #5	$79.99	13.608%	$90.875	$90.88	$90.90	$90.90
Purchase #6	$140.65	9.786%	$154.414	$154.41	$154.40	$154.40
Purchase #7	$194.86	8.461%	$211.3471	$211.35	$211.35	$211.30
7 purchase totals =	$923.21		$1,014.1230	$1,014.13	$1,014.10	$1,014.20